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1
Tsakiris, V. "Deformation twinning in austenitic steels." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371586.
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2
Naraghi, Reza. "Martensitic Transformation in Austenitic Stainless Steels." Thesis, KTH, Metallografi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-37214.
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Martensitic transformation is very important in austenitic stainless steels where the transformation induced plasticity phenomenon provides a combination of good mechanical properties, such as formability and strength. However, the difficulty of predicting the material behaviour is one of the major drawbacks of these steels. In order to model this behaviour it is of great importance to be able to characterize the morphology, crystallography and the amount of different types of martensite. The morphology and crystallography of thermal and deformation induced lath martensite in stainless steels were re-examined by means of optical microscopy and electron backscatter diffraction (EBSD) technique. The experiments were performed on AISI301, 304 and 204Cu austenitic stainless steels. Plastic deformation was carried out by means of uniaxial tensile tests at the strain rate of to produce strain induced α’-martensite at a temperature ranging from 0 to 60ºC. An in-situ measurement of the martensite content was performed during the tensile testing using a Ferritescope to provide the necessary experimental values for modelling. Optical microscopy revealed the morphology of the strain induced α’-martensite as sets of thin parallel needles that go through the parent austenite grain and stop at the grain or annealing twin boundaries. Large amount of α’-martensite could be seen at the intersection of shear bands. However, considerable amount of α’-martensite was also observed when only one set of bands is activated. EBSD was successfully used to analyze the morphology and crystallography of martensite. The α’-martensite maintained the Kurdjumov-Sachs (K-S) orientation relationship with the austenite phase. Although all six possible variants did not appear within a single packet, one or two variants were often favoured out of six related to the specific {111} plane. The misorientations between the neighbouring variants were mainly <111> 60º or <110> 49.5º.
3
Stewart, John. "Pit initiation on austenitic stainless steels." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277798.
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4
Street, Steven Richard. "Atmospheric corrosion of austenitic stainless steels." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7390/.
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Atmospheric corrosion was investigated using electrochemical and droplet studies. The effects of changes in bulk solution concentration and local pit chemistry on pit propagation and repassivation of 304L and 316L stainless steels were investigated using \(in\) \(situ\) synchrotron X-radiation and electrochemical techniques. Radiography and zig-zag electrochemical sweeps showed that in dilute chloride solutions, partial passivation was observed to initiate locally and propagate across the corroding surface. This caused repassivation gradually rather than as a uniform event. In concentrated chloride solutions, repassivation did not show a sudden drop in current but rather a gradual decrease as potential swept down. Pitting behaviour was also affected by solution concentration. Dilute solutions showed metastable pitting followed by a sharp breakdown (pitting) potential. Concentrated solutions however showed no metastability and a gradual increase in current when pitting. To determine the cause of current oscillations in 304L artificial pits in NaCl:NaNO\(_3\) solutions near the repassivation potential, the salt layers were scanned \(in\) \(situ\) using XRD. The salt layer was confirmed to be FeCl\(_2\).4H\(_2\)O and no nitrate salt was found. A mechanism was suggested to explain the current oscillations in terms of partial passivation being undercut by the advancing corrosion front.
5
Kornegay, Cynthia E. "Impact fracture of austenitic stainless steels." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/50038.
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Industry is constantly searching for improved
materials for use in highly demanding applications. The
materials chosen must withstand a wide range of
temperatures and extended exposure in aggressive
environments, including hydrogen gas. Because of the
risk of catostrophe if brittle failure occurs, careful
material selection is imperative. Austenitic stainless
steels may be a likely choice for hydrogen service
because their behavior in high pressure hydrogen ranges
from no apparent damage to relevent, but generally small
ductility loss (13). Because of this Variation in
behavior, a single category cannot be established to
encompass all austenitic steels and studies must be
performed on each type of steel to determine its behavior
under specific circumstances. Two steels being currently
under consideration for use in hydrogen are Armco 21-6-9
and Tenelon, both are fully austenitic stainless steels
which may be used over a wide range of temperatures,
including service at liquid nitrogen temperature.Master of Science
incomplete_metadata
6
Rao, Ashwin. "Creep and anelastic deformation in austenitic steels." Thesis, Open University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524785.
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This study examinest he creepb ehaviour of austenitic steels under service temperatures, to determine the effect of creep on material performance. Nuclear power plant components are in regular use at temperatures greater than 450°C, where creep deformation plays a dominant role in limiting the lifetime of the material. The prime aim of this study was to characterise the effect of load-reductions on the creep behaviour of austenitic steels (AlSI type 316H). In-service materials seldom operate at a constant load and/or temperature. The supply demand, maintenance operations, refuelling, etc. will result in large variation of load and temperature acting on the material. Experiments where load/temperature removals during a creep test were therefore conducted. These unloading procedures result in material recovery of the accumulated creep strain (anelasticity). This phenomenon will influence the material properties such as creep life and ductilities. Creep life was found to increase by 2-3 times whereas creep ductilities decreased by 50% when compared to steady-load creep data under identical conditions. The occurrence of anelasticity suggested the presence of a material backstress. The origin and evolution of this internal stress was investigated using neutron diffraction and TEM microscopy. Lattice strain measurements were conducted in-situ using neutron diffraction during a creep test which consisted of load/unload cycles. Experimental results suggest that creep strain is equivalent to plastic strain at a granular level. The data also shows intergranular micro-stressesa re introduced into the material by primary creep. Anisotropic behaviour of the individual crystal planes results in formation of tensile and compressive intergranular stressesin individual grain families. Residual compressives tressesd rive this anelastic deformation. TEM examinations of samples stopped during the unload show changes in dislocation and precipitate morphologies during the plastic strain recovery phase. Evidence of a changing dislocation substructure during the load-reduction period was found. Examinations have also shown carbide densities change during the unload. Pipe diffusion is a possible mechanism which can be used to explain this occurrence. The changing precipitate and dislocation state will influence the strengthening mechanisms, which in-turn will affect the deformation characteristics. These microstructural observations were introduced into a damage mechanics model. Predictions of material behaviour using this model have shown good agreement with experimental data. Outcomes of this project, have established that changes in creep deformation mechanisms will greatly influence material properties. Deformation history of the material will affect the intergranular stress state which in turn will affect the elastic and plastic response of the material. The effect of plastic strain history must be considered and incorporated accounted in any design and assessment procedure.
7
Young, Chune-Ching. "Transformation toughening in phosphocarbide-strengthened austenitic steels." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/77693.
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8
Hopkin, Gareth John. "Modelling anisothermal recrystallization in austenitic stainless steels." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/221867.
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9
Clausen, Bjoern, and risoe@risoe dk. "Characterisation of polycrystal deformation by numerical modelling and." Thesis, Risoe National Laboratory, 1999. http://www.risoe.dk/rispubl/AFM/ris-r-985.htm.
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10
Sandström, Rolf, Muhammad Farooq, and Joanna Zurek. "Basic creep models for a 25Cr20NiNbN austenitic stainless steels." KTH, Materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122155.
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Basic models for solid solution and precipitation hardening during creep are presented for the austenitic stainless steels 25Cr20NiNbN (TP310HNbN, HR3C, DMV310N). The solid solution hardening is a result of the formation of Cottrell clouds of solutes around the dislocations. In addition to slowing down the creep, the solutes increase the activation energy for creep. The increase in activation energy corresponds to the maximum binding energy between the solutes and the dislocations. The formation of fine niobium nitrides during service enhances the creep strength. It is found that the nitrides have an exponential size distribution. In the modelling the critical event is the time it takes for a dislocation to climb over a particle. The creep models can accurately describe the observed time and temperature of the creep rupture strength.
11
Galloway, Alexander M. "The weldability of nitrogen enriched austenitic stainless steels (316LN)." Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423871.
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12
Guo, Liya. "Atmospheric localised corrosion of type 304 austenitic stainless steels." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6458/.
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Atmospheric localised corrosion of stainless steel has been investigated under salt droplets containing a mixture of MgCl2 and NaCl between the deliquescence relative humidity of the two salts where there was precipitation of NaCl crystals. Dish-shaped pits and crevice-like attack could be observed. Effects of the change of relative humidity (RH) have been studied. A pit that has grown at 33% RH for 1 day will tend to repassivate when the RH is increased to 85% while pits grown at 33% RH for 3 weeks may not repassivate at 85% RH and can continue to grow when the RH is returned to 33%. A pit that has grown at 33% RH can continue to grow after 1 day at 12% RH if the RH is returned to 33%. RH fluctuations, either to low or high RH, lead to greater number of pits. Using the 1D artificial pit method, a potential sweep method was developed to investigate the repassivation process of pits in concentrated solutions, representative of atmospheric conditions. The onset of repassivation is defined as the point where there is no increase in current with an increase in potential. It has been found that repassivation takes place when the concentration of MgCl2 is lower than 3.2 M (equivalent to 64% RH) while there is no repassivation for 3.5 M and 4 M MgCl2 (equivalent to 59% RH and 50% RH respectively). A range of the repassivation potential and the critical metal ion concentration to prevent pits from repassivation was determined.
13
Stavehaug, Frode 1958. "Transformation toughening of [gamma][prime]-strengthened metastable austenitic steels." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/103191.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990.On t.p. "[gamma]" is the original Greek letter; "[prime]" is the mathematical symbol. Vita.
Includes bibliographical references (leaves 162-166).
by Frode Stavehaug.
Ph.D.
14
Sourmail, Thomas. "Simultaneous precipitation reactions in creep-resistant austenitic stainless steels." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/221868.
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15
Phan, Dan. "Atmospheric-Induced stress corrosion cracking of Austenitic Stainless Steels." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508598.
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16
Onyuna, Musa Omollo. "Deformation behaviour and martensitic transformations in metastable austenitic steels and low alloyed multiphase steels." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:swb:105-7223495.
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Es wurden die Mikrostruktur und die mechanischen Eigenschaften bedingt durch dehnungsinduzierte Martensitbildung im metastabilen austenitischen Stahl X5CrNi18.10 und in einem niedrig legierten Mn-Si-Al Stahl untersucht. Dazu wurden Zugversuche bei verschiedenen Temperaturen durchgeführt. Für den Stahl X5CrNi18.10 wird auf der Grundlage der Arbeit von Ludwigson und Berger ein Modell zur Beschreibung des Umwandlungsverhaltens als Funktion der Dehnung und der Temperatur entwickelt. Es kann weiterhin gezeigt werden, dass die erreichbare Gleichmaßdehnung in diesen Stahl durch eine maximal ertragbare Umformarbeit bestimmt wird. Die erhaltenen Fließkurven konnten mit Hilfe der FEM und einer modifizierten Mischungsregel für die Festigkeit erfolgreich modelliert werden. Die Ergebnisse für den Mn-Si-Al Stahl zeigen, dass neben dem Restaustenit, das Verbundverformungsverhalten der anderen Gefügebestandteile (Ferrit, Bainit, Martensit) wichtige Faktoren für die Optimierung der mechanischen Eigenschaften darstellen.
17
Jepson, Mark A. E. "Oxidation of austenitic and duplex stainless steels during primary processing." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/4435.
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18
Stringfellow, Richard Graham. "Mechanics of strain-induced transformation toughening in metastable austenitic steels." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13714.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1991.Title as it appears in the Feb. 1991 M.I.T. Graduate List: Mechanics of transformation toughening in metastable austenitic steels.
Includes bibliographical references (leaves 266-272).
by Richard Graham Stringfellow.
Ph.D.
19
Masters, G. L. "Crevice corrosion of austenitic and duplex stainless steels in seawater." Thesis, Cranfield University, 1994. http://dspace.lib.cranfield.ac.uk/handle/1826/11288.
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Duplex stainless steels are finding increasing use in seawater
applications, but are prone to attack by crevice corrosion. A mechanism of
deaeration and acidification is thought to produce locally aggressive conditions
within the crevice. A variety of experimental techniques were therefore used
to investigate the crevice corrosion resistance of some commercial duplex
stainless steels in seawater and other, more aggressive Cr-containing
environments. The established marine grade 316L austenitic stainless steel
was used for reference purposes. The investigations provided both
quantitative data regarding alloy performance, and qualitative observations
regarding the attack mechanism.
The crevice corrosion resistance of the duplex stainless steels was
shown to be superior to that of 316L, and to increase with (Cr + N) content.
Electrochemical polarisation scans demonstrated the importance of
dissolved 02 in the seawater in maintaining a protective passive film on these
alloys. Active peak current density, a measure of the severity of attack, was
shown to increase with decreasing pH. In a simulated crevice solution, the
duplex alloys were shown to exhibit both a narrower active range and lower
peak current density than 316L.
Potentiostatic tests showed weight loss to be an order of magnitude
lower for the duplex alloys. Measured weight losses were in agreement with
those predicted from polarisation data. The technique suggested that cathodic
protection potentials as noble as -600 mV (SCE) may be sufficient to protect
duplex stainless steels in seawater. Metallographic observation and electron
beam analysis showed that the attack mode is potential dependent, with
ferrite and austenite preferentially attacked at more active and noble potentials
respectively.
Real time tests showed that the internal crevice pH of austenitic
stainless steel could fall to as low as 1.3. The rise in corrosion current was
found to be a reliable indicator of attack, and was consistent with measured
weight loss. Potential shifts were found to be relatively insensitive indicators
of breakdown.
20
Al-Shahrani, Saeed. "Effect of surface finish on fatigue of austenitic stainless steels." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/effect-of-surface-finish-on-fatigue-ofaustenitic-stainless-steels(6acdedf2-4211-433b-b37a-2846dc6138d2).html.
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The effect of surface finish on fatigue limit of two types of austenitic stainless steels (AISI 304L and AISI 316L) has been investigated. Fatigue specimens having two different surface conditions were obtained by changing the final cutting condition; annealing was performed to separate the residual stress effects from surface roughness. Electropolished samples were tested as a reference for each material. A generic mechanistic model for short fatigue crack propagation proposed by Navarroand Rios (N-R model) was implemented to assess its suitability for predicting the fatigue behaviour of specimens with various controlled surface conditions, obtained by machining. The surface/material properties required to implement this model were obtained by electron backscatter diffraction (EBSD), surface profilometry, hardness testing and X-ray diffraction residual stress measurement. The fatigue limits were determined using rotating-bending by means of the staircase method. The fatigue limits predicted by the N-R fatigue model were compared with the results of the fatigue tests. There was no agreement between the prediction and observations, indicating that the original form of the N-R model is not appropriate for austenitic stainless steels. In AISI 304L, the surface residual stresses are the dominant parameter, allowing prediction of the effects of machining on fatigue resistance while, the surface roughness developed by machining has no significant effect. In AISI 316L, the effect of surface roughness is found to be negligible, with a weaker effect of surface residual stress than has been observed for AISI 304L. Crack nuclei in run-out (>107 cycles) fatigue tests were observed to arrest at twins and martensite packets, developed by fatigue in AISI 316L and AISI 304L, respectively. Good agreement with experiments was achieved by using a modification to the fatigue model, which takes account of the observed effect of the plastic deformation on the microstructure.
21
Salinas-Bravo, Victor Manuel. "Pitting and stress corrosion cracking of duplex stainless steels." Thesis, University of Manchester, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493165.
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22
Farooq, Muhammad. "Strengthening and degradation mechanisms in austenitic stainless steels at elevated temperature." Doctoral thesis, KTH, Materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122158.
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With rapid economic developments and rising living standards, the demand for electricity all over the world is greatly increased. Due to high fuel costs, the steam boilers with higher steam temperature and pressure are needed to decrease the cost of power generation throughout the world extensively. In recent years, human awareness of the gradual strengthening of environmental protection increases, therefore to reduce the CO2 emissions the power generation efficiency needs to be improved. The development of high temperature materials with improved creep rupture strength and oxidation resistance is critically needed. Materials for these demanding conditions are austenitic stainless steels such as 310, 310NbN and Sanicro 25. Fundamental models have been developed for the precipitation of coarse particles during long time ageing of austenitic stainless steels and the influence of the particles on the mechanical properties. The models have been verified by ageing experiments. The austenitic stainless steel 310 was aged for up to 5000 h at 800 ºC. The precipitation models could satisfactorily describe the influence of ageing time on the radii and the volume fractions of particles. Models for the influence of the coarse precipitates on the tensile properties and the toughness were developed and reproduce the measured mechanical properties without the use of any fitting parameters. These developed models were utilised to investigate the influence of bands on ductility and toughness at room temperature. Up to 10 % σ-phase was observed to precipitate, which has a pronounced influence of the mechanical properties. Thermodynamic analysis demonstrated that the amount of precipitates due to ageing can significantly be reduced if the nitrogen or the carbon content is increased. Microstructure investigations of austenitic stainless steel 310NbN and Sanicro 25 were carried out by light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The austenitic stainless steel 310NbN was aged for up to 10000 h at 650 and 750 ºC. The austenitic stainless steel Sanicro 25 was also aged for up to 10000 h at 650 and 700 ºC. Phase fractions and mean radii evolution of precipitates were calculated and compared to the experimental results. Size distributions of the precipitates in these steels were determined. Models for the different contributions to the creep strength have been applied: i) a recovery creep model for the dislocation hardening; ii) a climb controlled model for the precipitation hardening; iii) solid solution hardening from Cottrell clouds of solutes around the dislocations, and iv) A modified Dobes model for the effective stress. The total contributions can describe the experimental creep strength satisfactorily without the use of adjustable parameters.QC 20130517
23
Bromley, Darren Michael. "Hydrogen embrittlement testing of austenitic stainless steels SUS 316 and 316L." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/925.
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The imminent emergence of the hydrogen fuel industry has resulted in an urgent mandate for very specific material testing. Although storage of pressurized hydrogen gas is both practical and attainable, demands for increasing storage pressures (currently around 70 MPa) continue to present unexpected material compatibility issues. It is imperative that materials commonly used in gaseous hydrogen service are properly tested for hydrogen embrittlement resistance. To assess material behavior in a pressurized hydrogen environment, procedures were designed to test materials for susceptibility to hydrogen embrittlement.
Of particular interest to the field of high-pressure hydrogen in the automotive industry, austenitic stainless steels SUS 316 and 316L were used to validate the test programs. Tests were first performed in 25 MPa helium and hydrogen at room temperature and at -40°C. Tests in a 25 MPa hydrogen atmosphere caused embrittlement in SUS 316, but not in 316L. This indicated that alloys with higher stacking fault energies (316L) are more resistant to hydrogen embrittlement. Decreasing the test temperature caused slight embrittlement in 316L and significantly enhanced it in 316. Alternatively, a second set of specimens was immersed in 70 MPa hydrogen at 100°C until reaching a uniform concentration of absorbed hydrogen. Specimens were then loaded in tension to failure to determine if a bulk saturation of hydrogen provided a similar embrittling effect. Neither material succumbed to the effects of gaseous pre-charging, indicating that the embrittling mechanism requires a constant supply of hydrogen at the material surface rather than having bulk concentration of dissolved hydrogen. Permeation tests were also performed to ensure that hydrogen penetrated the samples and to develop material specific permeation constants.
To pave the way for future work, prototype equipment was constructed allowing tensile or fatigue tests to be performed at much higher hydrogen pressures. To determine the effect of pressure on hydrogen embrittlement, additional tests can be performed in hydrogen pressures up to 85 MPa hydrogen. The equipment will also allow for cyclic loading of notched tensile or compact tension specimens for fatigue studies.
24
Benyahya, Matlub Mohammed. "Corrosion behaviour of austenitic steels in basic thiosulfate gold leaching environments." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44373.
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Thiosulfate leaching of gold is being proposed as an environmentally friendly alternative to
the dominant cyanide-leaching technology. Thiosulfate leaching is, to a large extent, dependent
on the availability of materials of construction. There are indications that materials of
construction could be a major issue if not addressed; particularly their corrosion resistance.
Therefore, understanding the corrosion behaviour of materials of construction, such as stainless
steels, in this medium is critical to the future development and acceleration of industrial
implementation of this new technology.
The debate surrounding the use of cyanide in the mining industry has fuelled considerable
investigation into the development of some more environmentally benign alternatives. The
thiosulfate process has been widely accepted by researchers around the world as a potential
alternative lixiviant for the leaching and recovery of gold. Moreover, sodium thiosulfate is
relatively nontoxic and, consequently, from an environmental standpoint, has a definite
advantage over cyanide. Comparing reagent unit costs, sodium thiosulfate is far cheaper than
sodium cyanide. Thus, with similar or even slightly higher lixiviant consumption, the application
of thiosulfate for gold recovery can be economical and compete directly with cyanidation.
‘Rust never sleeps!’, so says a popular song. In a broad sense, corrosion appears to be the
reverse process of extraction. In this process, most metals tend to presume a chemicallycombined
state rather than a pure metallic form achieving, in the process, the most energy stable
iii
form possible. Thus, freshly-extracted metals, as well as finished metallic products, tend to deteriorate when exposed to certain environments. Thiosulfate has been identified as such an environment in mining and other industries, where thiosulfate-dominated processes, such as thiosulfate gold leaching, are strongly believed to highly promote localized corrosion.
In this work, the pitting corrosion behaviour of 304- and 316-type stainless steels were studied using cyclic polarization techniques and electrochemical impedance spectroscopy (EIS) run on a thiosulfate system at several pH and temperature levels in the presence and absence of chloride ions. The stainless steels studied were found to show similar general corrosion behaviour with varying degrees of corrosion resistance to pitting as control variables were regularly perturbed. The results indicate that SS316 has a relatively lower corrosion rate and is more resistant to localized corrosion than SS304 under the conditions considered.
The presence of thiosulfate seems to activate both anodic and cathodic current densities of steel in chloride solutions. The higher the thiosulfate concentration is, the greater the current densities. In addition, for both alloys, the corrosion rate generally increases as the magnitude of the variables is increased; except when the content of chloride ions is altered. Thiosulfate seems to promote passivation in the presence of chloride ions and deter interaction of those ions with the surface of the metal alloys by the formation of an adsorption layer of sulfur that seems to protect the metal surface.
25
Olsson, Malin. "Thermodynamic modeling of the stacking fault energy in austenitic stainless steels." Thesis, KTH, Termodynamisk modellering, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148660.
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The stacking fault energy (SFE) of seven austenitic stainless steels with the compositions x(Cr)=20 at%, 8≤x(Ni)≤20 at% and 0≤x(Mn)≤8 at% have been calculated at room temperature using the thermodynamics-based Olson and Cohen modeling approach [1]. Modeling has been performed using the TCFE7 database together with the Thermo-Calc 3.0 software. Experimental SFE values from transmission electron microscopy (TEM) measurements and theoretical SFE values from ab initio calculations were used for comparison. The results of the SFE from TCFE7 were not in agreement with the values reported in the literature. After an evaluation of the thermodynamic parameters in the database, a new assessment of the SFE in the ternary and quaternary Fe-Cr-Ni and Fe-Cr-Ni-Mn system was proposed which resulted in SFE values in fairly good agreement with the literature.
26
Al-Amr, Abdulaziz. "Mechanical behavior and structure of passive films on austenitic stainless steels." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Dissertations/Spring2005/a%5Falamr%5F042505.pdf.
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Mansoux, Hilaire. "Experimental determination of radiation induced segregation susceptibility in austenitic stainless steels." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12131.
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Yu, Lun Ph D. Massachusetts Institute of Technology. "The environmental effect on corrosion fatigue behavior of austenitic stainless steels." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/120869.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Corrosion fatigue is a multivariate challenge that threatens the lifetime of service of nuclear power plant materials, especially austenitic stainless steels. Both enhancement and retardation of crack growth have been observed in laboratory tests. This thesis work performs high temperature autoclave testing, post-test characterization and mechanistic modeling to understand the corrosion fatigue behavior of austenitic stainless steels in simulated light water reactor (LWR) environments. Crack growth rate (CGR) data were generated from the autoclave testing on low (0.001 wt.%) and high (0.03 wt.%) sulfur content heat 1T compact tension (CT) specimens. Tests were controlled under constant K (22-35 MPa [square root of]m) with load ratio of 0.7 and sawtooth waveform (85% rise vs. 15% fall), and at pH =10 and 288 °C with system pressure of 9.54 MPa. Crack enhancement was observed in low sulfur content heat specimens, and the CGR increases as the loading rise time increases. The fracture surfaces of low sulfur content heat specimens showed transgranular features with facets ("river pattern") and few oxide particles. Crack retardation was observed in high sulfur content heat specimens, and the CGR decreases as the loading rise time increases. The fracture surfaces of high sulfur content heat specimens showed distinct features at different rise time step. Transgranular features ("river pattern") were observed at short rise time step, while non-descript surfaces with fine octahedral oxide particles were observed at long rise time step. Additionally, tests in deuterium water were performed to enable measurements on hydrogen/deuterium concentrations in specimens using ToF-SIMS and hot vacuum extraction techniques. Deuterium pick-up from the testing environment was observed, and the enrichment of deuterium/hydrogen ahead of crack tip was also observed. Controlled experiments were also conducted, where specimens were baked prior to the autoclave testing to remove the residual internal hydrogen. Such heat treatment removing the internal hydrogen was found to not affect the crack growth behavior. Dissolved gases, hydrogen and argon respectively, were bubbled into system during the autoclave tests, and they resulted in similar crack growth behaviors. Modeling indicates that there exists an enhancement mechanism other than corrosion mass removal driving the crack growth in simulated LWR environments. Possibly it comes from the effect of corrosion-generated hydrogen. Retardation behavior and experimental observations could be understood and explained by concept and modeling of corrosion blunting. The results suggest excess conservatism of current ASME standards N-809 for high sulfur content austenitic stainless steels.
by Lun Yu.
Ph. D.
29
Molnár, Dávid Sándor. "Generalised stacking fault energy and plastic deformation of austenitic stainless steels." Licentiate thesis, KTH, Tillämpad materialfysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233565.
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Austenitic stainless steels are primarily known for their exceptional corrosion resistance. They have the face centred cubic (FCC) structure which is stabilised by adding nickel to the Fe-Cr alloy. The Fe-Cr-Ni system can be further extended by adding other elements such as Mn, Mo, N, C, etc. in order to improve the properties. Since austenitic stainless steels are often used as structural materials, it is important to be able to predict their mechanical behaviour based on their composition, microstructure, magnetic state, etc. In this work, we investigate the plastic deformation behaviour of austenitic stainless steels by theoretical and experimental approaches. In FCC materials the stacking fault energy (SFE) plays an important role in the prediction of the deformation modes. Based on the magnitude of the SFE different deformation modes can be observed such as martensite formation, deformation twinning, dissociated or undissociated dislocation glide. All these features influence the behaviour differently, therefore it is desired to be able to predict their occurrence. Alloying and temperature have strong effect on the SFE and thus on the mechanical properties of the alloys. Several models based on the SFE and more recently on the so called generalised stacking fault energy (GSFE or γ-surface) are available to predict the alloy's affinity to twinning and the critical twinning stress representing the minimum resolved shear stress required to initiate the twinning deformation mechanism. One can employ well established experimental techniques to measure the SFE. On the other hand, one needs to resort to ab initio calculations based on density functional theory (DFT) to compute the GSFE of austenitic steels and derive parameters like the twinnability and the critical twinning stress. We discuss the effect of the stacking fault energy on the deformation behaviour for two different austenitic stainless steels. We calculate the GSFE of the selected alloys and based on different models, we predict their tendency for twinning and the critical twinning stress. The theoretical predictions are contrasted with tensile tests and electron backscatter diffraction (EBSD) measurements. Several conventional and in situ tensile test are performed to verify the theoretical results. We carry out EBSD measurements on interrupted and fractured specimens and during tensile tests to closely follow the development of the microstructure. We take into account the role of the intrinsic energy barriers in our predictions and introduce a new and so far unique way to experimentally obtain the GSFE of austenitic stainless steels. Previously, only the SFE could be measured precisely by well-designed experiments. In the present thesis we go further and propose a technique that can provide accurate unstable stacking fault energy values for any austenitic alloy exhibiting twinning.Austenitiska rostfria stål är främst kända för sin exceptionella korrosionsbeständighet. De har en ytcentrerad kubisk (FCC) struktur som stabiliseras genom att nickel tillsätts till Fe-Cr legeringen. Fe-Cr-Ni-systemet kan utökas ytterligare genom tillsats av andra element såsom Mn, Mo, N, C, etc. för att förbättra egenskaperna. Eftersom austenitiska rostfria stål ofta används som konstruktionsmaterial är det viktigt att kunna förutsäga deras mekaniska egenskaper baserat på deras sammansättning, mikrostruktur, magnetiska tillstånd, etc. I denna avhandling undersöker vi det plastiska deformationsbeteendet hos austenitiska rostfria stål både teoretiskt och experimentellt. I FCC material spelar staplingsfelsenergin (SFE) en viktig roll vid förutsägelsen av deformationsmekanism. Baserat på storleken av SFE kan olika deformationsmekanismer observeras, såsom martensitbildning, tvillingbildning, dissocierad eller odissocierad dislokationsglidning. Alla dessa funktioner påverkar beteendet på olika sätt, därför är det önskvärt att kunna förutsäga deras förekomst. Legering och temperatur har stark inverkan på SFE och därmed legeringarnas mekaniska egenskaper. Flera modeller, baserade på SFE och mer nyligen på den så kallade generaliserade staplingsfelenergin (GSFE eller γ-surface), är tillgängliga för att förutsäga legeringens benägenhet till tvillingbildning och den kritiska spänning som representerar den minsta upplösta skjuvspänningen som krävs för att initiera tvillingbildning. Man kan använda ab initio beräkningar baserade på täthetsfunktionalteori (DFT) för att beräkna GSFE för austenitiska stål och härleda parametrar som twinnability och kritisk tvillingsspänning. Vi diskuterar effekten av staplingsfelenergi på deformationsbeteendet för två olika austenitiska rostfria stål. Vi beräknar GSFE för de valda legeringarna och baserat på olika modeller, förutsäger vi deras tendens till tvillingbildning och den kritiska tvillingsspänningen. De teoretiska förutsägelserna jämförs med resultat från dragprov och bakåtspridd elektron diffraktion (EBSD). Flera konventionella och in situ dragprov utfördes för att verifiera de teoretiska resultaten. Vi utförde EBSD-mätningar på dragprov som avbrutits vid olika töjningar och efter brott samt med in situ dragprov för att följa utvecklingen av mikrostrukturen noggrant. Vi tar hänsyn till de inre energibarriärernas roll i våra förutsägelser och presenterar ett nytt sätt att experimentellt få GSFE av austenitiska rostfria stål. Tidigare kunde endast SFE mätas tillförlitligt genom väl utformade experiment. I den aktuella avhandlingen går vi vidare och föreslår en teknik som kan ge noggranna värden för den instabila staplingsfelenergin för alla austenitiska legeringar som uppvisar tvillingbildning.
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Bruemmer, Stephen M. "Quantitative measurement and modeling of sensitization development in stainless steels /." Full text open access at:, 1988. http://content.ohsu.edu/u?/etd,165.
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Duffey, Matthew James. "Metallurgical Characterization and Weldability Evaluation of Ferritic and Austenitic Welds in Armored Steels." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460910681.
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Cardoso, Jorge Luiz. "Evaluation of the precipitation of secondary phases on CO2 environment corrosion resistance of austenitic and super austenitic stainless steels." reponame:Repositório Institucional da UFC, 2016. http://www.repositorio.ufc.br/handle/riufc/18440.
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CARDOSO, J. L. Evaluation of the precipitation of secondary phases on CO2 environment corrosion resistance of austenitic and super austenitic stainless steels. 2016. 133 f. Tese (Doutorado em Ciência de Materiais) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2016.Submitted by Hohana Sanders (hohanasanders@hotmail.com) on 2016-07-15T13:48:21Z No. of bitstreams: 1 2016_tese_jlcardoso.pdf: 8753874 bytes, checksum: a423033a537ecd65f676406b27740c08 (MD5)
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Austenitic stainless steels are widely used in several applications including the manufacture of pipelines for the oil and gas industry. This work discusses the corrosion behavior of austenitic and super austenitic stainless steels in CO2-containing environments. The steels used in this work were the AL-6XN PLUS™ (UNS Designation N08367) and 904L (UNS Designation N08904) super austenitic stainless steels. Two conventional austenitic stainless steels, 316L (UNS S31600/ S31603) and 317L (UNS S31703) were also used for comparison purposes. Potentiodynamic polarization measurements were taken in CO2-saturated synthetic oil field formation water, deaerated with nitrogen to simulate some conditions in the pre-salt region. Potentiostatic measurements were also carried out to evaluate the corrosive level of the solution without the presence of CO2. Pressurized experiments using autoclave in CO2-containing environment and in synthetic air environment were also conducted to evaluate the corrosion resistance of the alloys when pressure and temperature act together. Heat treatments at high temperatures between 600 °C and 760°C in different ranges of time were also conducted to evaluate the possible sigma phase precipitation and its effect on the corrosion resistance. The AL-6XN PLUS™ and 904L super austenitic stainless steels showed a good performance in CO2-containing environment. The AL-6XN PLUS™ steel also exhibited the best performance in the pressurized experiments. The conventional 316L and 317L steels showed susceptibility to pitting and crevice corrosion. The results showed that the conventional alloys are not suitable for the use in CO2-containing environment under severe conditions. Pitting potential of the 316L alloy was affected by the pH of the solution in CO2-saturated solution. No sigma phase precipitated in the heat treatments for the range of time used indicating that its precipitation kinetics in austenitic stainless steels is very slow. This result is an advantage when working with austenitic stainless steels for long periods of exposure at high temperatures.
Os aços inoxidáveis austeníticos e super austenític os são amplamente utilizados na fabricação de tubulações na industria de petróleo e gás. Esse trabalho discute o comportamento da corrosão de aços inoxidáveis austeníticos e super a usteníticos em meio contendo CO 2 . Os aços usados nesse trabalho foram os aços super aust eníticos AL-6XN PLUS™ (Designação UNS N08367) e 904L (Designação UNS N08904). Dois aç os austeníticos convencionais, 316L (UNS S31600/ S31603) e 317L (UNS S31703), tamb ém foram usados para comparação. Foram realizadas medidas de polarização potenciodinâmica em água artificial de formação de poço de petróleo saturada com CO 2 e desaerada com nitrogênio para simular algumas condições do pré-sal. Foram também realizad as medidas potenciostáticas para avaliar o nível corrosivo da solução sem a presença de CO 2 . Experimentos pressurizados usando autoclaves em meio contendo CO 2 e ar sintético também foram realizados para avalia r a resistência à corrosão das ligas quando pressão e t emperatura agem juntas. Foram realizados tratamentos térmicos em altas temperaturas entre 60 0 °C e 760 °C em diferentes faixas de tempo para avaliar a formação de fase sigma e seu e feito na resistência à corrosão. Os aços super austeníticos AL-6XN PLUS™ e 904L mostraram um a boa performance em meio contendo CO 2 . O aço AL-6XN PLUS™ também exibiu uma boa performa nce nos experimentos pressurizados. Os aços convencionais 3 16L e 317L apresentaram susceptibilidade à corrosão por pites e frestas. Os resultados mostraram que os aços convencionais não são apropriados para uso em meio contendo CO 2 sob condições severas. O potencial de pite do aço 316L foi afetado pelo pH d a solução em meio saturado com CO 2 . Não houve precipitação de fase sigma nos tratamento s térmicos para as faixas de tempo usadas indicando que sua cinética de precipitação e m aços inoxidáveis austeníticos é muito lenta. Esse resultado é uma vantagem ao se trabalha r com aço inoxidáveis austeníticos em logos períodos de exposição em altas temperaturas.
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Alsarraf, Jalal. "Hydrogen embrittlement susceptibility of super duplex stainless steels." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/4562.
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This thesis describes the metallurgical and environmental factors that influence hydrogen embrittlement of super duplex stainless steels and presents a model to predict the rate at which embrittlement occurs. Super duplex stainless steel has an austenite and ferrite microstructure with an average fraction of each phase of approximately 50%. An investigation was carried out on the metallurgical and environmental factors that influence hydrogen embrittlement of super duplex stainless steels. Tensile specimens of super duplex stainless steel were pre-charged with hydrogen for two weeks in 3.5% NaCl solution at 50º C at a range of applied potentials to simulate the conditions that exist when subsea oilfield components are cathodically protected in seawater. The pre-charged specimens were then tested in a slow strain rate tensile test and their susceptibility to hydrogen embrittlement was assessed by the failure time, reduction in cross-sectional area and examination of the fracture surface. The ferrite and austenite in the duplex microstructures were identified by analysing their Cr, Ni, Mo and N contents in an electron microscope, as these elements partition in different concentrations in the two phases. It was shown that hydrogen embrittlement occurred in the ferrite phase, whereas the austenite failed in a ductile manner. An embrittled region existed around the circumference of each fracture surface and the depth of this embrittlement depended on the hydrogen charging time and the potential at which the charging had been carried out. The depth of embrittlement was shown to correlate with the rate of hydrogen diffusion in the alloy, which was measured electrochemically using hydrogen permeation and galvanostatic methods. A two-dimensional diffusion model was used to calculate the hydrogen distribution profiles for each experimental condition and the model could be employed to provide predictions of expected failure times in stressed engineering components.
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Ostratický, Marek. "Makrosegregace a mikrosegregace v austenitických CrNi ocelích." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-319261.
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This diploma thesis deals with segregation cycles in austenitic CrNi steels. In first section deals with theory of macrosegregation and microsegregation cycles. The second part is focused on this cycles in experimental casting. Macrosegregation was measured by spectrometric analyser and by MAGMA simulation program. Microsegregation was measured by electron microscope. The aim of this diploma thesis is verify the influence of setting conditions on heterogenity chemical composition in austenitic CrNi steel. For experimental casting with a wall thickness of about 500 mm will be verified effect of the setting time, residence time between solid and liquid phases and others parameters for macrosegregation and microsegregation in selected elements.
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Jani, Shilesh Chandrakant. "A mechanistic study of transgranular stress corrosion cracking of austenitic stainless steels." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/11236.
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Schwind, Martin. "Diffusion in Multiphase and Multicomponent Alloys with Applications to Austenitic Stainless Steels." Doctoral thesis, KTH, Materials Science and Engineering, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3280.
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McGinnis, Alexander L. "Diffusion Couple Alloying of Refractory Metals in Austenitic and Ferritic/Martensitic Steels." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6832.
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This thesis utilized the diffusion couple approach to evaluate the addition of molybdenum, niobium, tantalum, and tungsten to 316 stainless (316SS) and alloy HT9 steels. Refractory elements have been previously studied as alloying candidates to mitigate problems such as radiation-induced segregation, void swelling, and irradiation creep in reactor steels. Diffusion couples were characterized via energy dispersive x-ray spectroscopy (EDS) and nanoindentation to examine refractory element solubility, diffusivity, and the effects these elements have on hardness and elastic modulus in 316SS and alloy HT9. Molybdenum and tungsten samples showed significantly higher solubility and diffusivity than niobium and tantalum, with evidence of multiphase regions several hundred microns from the diffusion couple interface. Nanoindentation revealed evidence of hardening as a function of increasing concentration for some, but not all of the refractory elements. Diffusion of the refractory elements in alloy HT9 was significantly higher than in 316SS, which suggests that alloy HT9 retained its ferritic structure even at high temperatures, i.e., 1100C.
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Socrate, Simona. "Mechanics of microvoid nucleation and growth in high-strength metastable austenitic steels." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11257.
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Xie, Ruiwen. "Carbon Effect on Mechanical Properties in Austenitic Steels - A DFT-based Study." Licentiate thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-244853.
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To study the effect of carbon interstitials in austenitic steels on plastic deformation mechanisms is the main goal of the present thesis. Using first-principlesmethods, the generalized stacking fault energy (GSFE) of C-alloyed γ-Fe is firstcalculated. The GSFE curve includes several prominent stacking fault energiesthat are fundamental for, e.g, predicting critical twinning stress and twinnability. The C effect was previously investigated in γ-Fe assuming nonmagnetic(NM) state. However, paramagnetic (PM) state with local magnetic momentson each site and total magnetization equal to zero is a more appropriate description for austenites. The Exact Muffin-Tin Orbitals (EMTO) method is capableof modelling the PM state together with the Coherent Potential Approximation (CPA). We also compare the NM GSFEs of C-alloyed γ-Fe obtained fromEMTO and Vienna Ab initio Simulation Package (VASP) to evaluate the performance of EMTO on handling the C-interstitial structure. The EMTO resultsare verified to fit reasonably well with VASP results so the GSFE calculationfor the C-alloyed γ-Fe is further extended to the PM state.The influence of C interstitials on the GSFE for PM γ-Fe is significantly different from what is predicted for NM γ-Fe. Though the GSFE is increased byC addition for both NM and PM γ-Fe, the C-driven change on the GSFE ascompared to pure γ-Fe at the PM state deviates from that at the NM state:paramagnetism significantly weakens the C impact on the intrinsic stacking faultenergy while strengthens it on the unstable stacking fault energy as comparedto the hypothetical NM case. The different behaviours uncovered for the intrinsic and unstable stacking fault energies due to the presence of local magneticmoments is illustrated by the magnetic structures of the Fe-C alloys as a function of volume, which mainly emerged from the suppression effect of C on themagnetic moments of its adjacent Fe neighbours.Using the generalized stacking fault as an approximation for the partial dislocation core, we investigate the minimum energy path (MEP) for C diffusionin the dislocation core (i.e., for various displacement vectors ) for NM γ-Feusing VASP. In contrast to the common assumption of stationary interstitialatoms during the passage of fast-moving dislocations, a pair of partial dislocations moves C atoms forward on the slip plane by one full Burgers vector. Thisdissociated dislocation-mediated transport mechanism for C is a strain inducedprocess, which is present even when the normal thermally activated diffusion isinoperative. Moreover, at the stacking fault ribbon and especially near the partial dislocation core, the in-plane diffusion energy barriers for C are significantlyreduced compared to that in bulk, opening a fast diffusion pathway for C. Themagnetic effect is also indirectly considered for the in-plane C diffusion energybarrier by calculating the MEP in high-spin ferromagnetic (HS-FM) Fe and ferromagnetic (FM) Ni. It is concluded that the presence of magnetic couplingdoes not change this trend. Therefore, contrary to the previously suggestedmechanism based on the reorientation of Mn-C short range order, our resultsreveal that the fast pipe diffusion of C at the dissociated dislocations is primarily responsible for the dynamic strain aging (DSA) in Fe-Mn-C steels and themechanism for DSA-mediated formation of deformation twinning is proposed to understand the strain rate dependence of deformation twinning in the presenceof DSA.
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Guaytima, Gustavo M. "A study of Ni-Cu weld metals for joining austenitic stainless steels." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406888576.
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Sibanda, Mandla. "Evaluation of the formability properties of nitrogen alloyed metastable austenitic stainless steels." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/18216.
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Bibliography: pages 92-95.This study examines the formability of an AISI 301 based metastable austenitic stainless steel, in which nitrogen partially substitutes nickel. In order to understand the formability of the experimental alloys, the tensile behaviour of the alloys is characterised. The tensile properties of metastable austenitic stainless steels are governed by austenite stability which is related to alloy composition and test temperature. At certain alloy compositions, transformation induced plasticity (TRIP) occurs. TRIP depends on the manner in which deformation induced martensite forms in the steels. Incipient necking is resisted if the martensite forms gradually and selectively, preventing propagation of micronecks and microcracks. Tensile tests performed from -5 to 100°C were used to study the effect of TRIP on the ductility of these alloys and optimum tensile properties were obtained at room temperature. In addition, the effect of copper on TRIP and subsequently formability were ascertained using copper alloyed stainless steels. Important stretch formability parameters were obtained from the tensile test which is an intrinsic formability test. TRIP results in improved formability of metastable austenitic stainless steels, and a simulative Engelhardt test was performed to ascertain the effect of TRIP on drawability of the test alloys. It was found that alloys with TRIP characteristics exhibited good drawability and in all cases the test alloys had better limiting drawing ratios than AISI 304 stainless steel. Delayed cracking occurred in alloys with more than 0.2 percent nitrogen content and a low austenite stability, probably as a result of embrittlement of the deformation induced martensite by nitrogen. A study of the cavitation erosion of the test alloys was initiated because it is known that TRIP enhances cavitation erosion resistance in stainless steels. Results indicate that the metastable test alloys demonstrate superior erosion resistance when compared with the stable experimental alloys. Cavitation induced martensite was found in metastable alloys using x-ray diffraction.
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Kömi, J. (Jukka). "Hot ductility of austenitic and duplex stainless steels under hot rolling conditions." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514265602.
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Abstract
The effects of restoration and certain elements, nitrogen, sulphur, calcium and
Misch metal, on the hot ductility of austenitic, high-alloyed austenitic and
duplex stainless steels have been investigated by means of hot rolling, hot
tensile, hot bending and stress relaxation tests. The results of these different
testing methods indicated that hot rolling experiments using stepped specimens is
the most effective way to investigate the relationship between the softening and
cracking phenomena under hot rolling conditions. For as-cast, high-alloyed and
duplex stainless steels with a low impurity level, the cracking tendency was
observed to increase with increasing pass strain and temperature, being minimal
for the small strain of 0.1. No cracking occurred in these steels when rolled in
the wrought condition. It could be concluded that the cracking problems are only
exhibited by the cast structure with the hot ductility of even partially
recrystallised steel being perfectly adequate. However, the recrystallisation
kinetics of the high-alloyed austenitic stainless steels, determined by stress
relaxation and double-pass rolling tests, were found to be so slow that only
partial softening can be expected to occur between roughing passes under normal
rolling conditions. In the duplex steel, the restoration is fairly fast so that
complete softening can occur within typical interpass times in hot rolling, while
certain changes in the phase structure take place as well.
Sulphur was found to be an extremely harmful element in duplex stainless steel
with regard to their hot ductility so that severe cracking can take place with
sulphur content above 30 ppm. However, the effect of sulphur can be eliminated by
reducing its content and by calcium or Misch metal treatments that significantly
increase the number and decrease the average size of the inclusions. It seems
that the desulphurisation capacity of an element is the most important property
for assessing its usefulness in reducing the detrimental influence of sulphur.
The hot ductility of type 316L stainless steel determined by tensile tests was
found to be better for nitrogen content of 0.05 wt-% than 0.02%, while in
double-hit tensile tests the hot ductility values were identical. The mechanism
whereby nitrogen affects hot ductility remains unclear but a retarding effect on
static recrystallisation was observed.
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Sapiro, David O. "The Effects of Alloy Chemistry on Localized Corrosion of Austenitic Stainless Steels." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/1087.
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This study investigated localized corrosion behavior of austenitic stainless steels under stressed and unstressed conditions, as well as corrosion of metallic thin films. While austenitic stainless steels are widely used in corrosive environments, they are vulnerable to pitting and stress corrosion cracking (SCC), particularly in chloride-containing environments. The corrosion resistance of austenitic stainless steels is closely tied to the alloying elements chromium, nickel, and molybdenum. Polarization curves were measured for five commercially available austenitic stainless steels of varying chromium, nickel, and molybdenum content in 3.5 wt.% and 25 wt.% NaCl solutions. The alloys were also tested in tension at slow strain rates in air and in a chloride environment under different polarization conditions to explore the relationship between the extent of pitting corrosion and SCC over a range of alloy content and environment. The influence of alloy composition on corrosion resistance was found to be consistent with the pitting resistance equivalent number (PREN) under some conditions, but there were also conditions under which the model did not hold for certain commercial alloy compositions. Monotonic loading was used to generate SCC in in 300 series stainless steels, and it was possible to control the failure mode through adjusting environmental and polarization conditions. Metallic thin film systems of thickness 10-200 nm are being investigated for use as corrosion sensors and protective coatings, however the corrosion properties of ferrous thin films have not been widely studied. The effects of film thickness and substrate conductivity were examined using potentiodynamic polarization and scanning vibrating electrode technique (SVET) on iron thin films. Thicker films undergo more corrosion than thinner films in the same environment, though the corrosion mechanism is the same. Conductive substrates encourage general corrosion, similar to that of bulk iron, while insulating substrates supported only localized corrosion.
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Sapiro, David O. "The Effects of Alloy Chemistry on Localized Corrosion of Austenitic Stainless Steels." Thesis, Carnegie Mellon University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10639516.
Full textAbstract:
This study investigated localized corrosion behavior of austenitic stainless steels under stressed and unstressed conditions, as well as corrosion of metallic thin films. While austenitic stainless steels are widely used in corrosive environments, they are vulnerable to pitting and stress corrosion cracking (SCC), particularly in chloride-containing environments. The corrosion resistance of austenitic stainless steels is closely tied to the alloying elements chromium, nickel, and molybdenum. Polarization curves were measured for five commercially available austenitic stainless steels of varying chromium, nickel, and molybdenum content in 3.5 wt.% and 25 wt.% NaCl solutions. The alloys were also tested in tension at slow strain rates in air and in a chloride environment under different polarization conditions to explore the relationship between the extent of pitting corrosion and SCC over a range of alloy content and environment. The influence of alloy composition on corrosion resistance was found to be consistent with the pitting resistance equivalent number (PREN) under some conditions, but there were also conditions under which the model did not hold for certain commercial alloy compositions. Monotonic loading was used to generate SCC in in 300 series stainless steels, and it was possible to control the failure mode through adjusting environmental and polarization conditions. Metallic thin film systems of thickness 10-200 nm are being investigated for use as corrosion sensors and protective coatings, however the corrosion properties of ferrous thin films have not been widely studied. The effects of film thickness and substrate conductivity were examined using potentiodynamic polarization and scanning vibrating electrode technique (SVET) on iron thin films. Thicker films undergo more corrosion than thinner films in the same environment, though the corrosion mechanism is the same. Conductive substrates encourage general corrosion, similar to that of bulk iron, while insulating substrates supported only localized corrosion.
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NEVES, MAURICIO D. M. das. "Soldagem de varetas combustiveis de aco inoxidavel para reatores nucleares." reponame:Repositório Institucional do IPEN, 1986. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9877.
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Dissertacao (Mestrado)
IPEN/D
Universidade Estadual de Campinas - UNICAMP/SP
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Betrabet, Hemant Shridhar. "The influence of nitrogen on the sensitization and microstructural properties of AISI 304 stainless steels /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603219054.
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Hargreaves, Martin Lawrence. "Digital processing of ultrasound signals back-scattered from coarse grained austenitic stainless steel." Thesis, Keele University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329895.
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Yang, Qi. "Effects of hydrogen on passivity and corrosion related behavior of austenitic stainless steels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0010/NQ59701.pdf.
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Iyer, Venkatramani S. "Effect of residual stress gradients in austenitic stainless steels on stress corrosion cracking." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/42119.
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The effect of the residual stresses developed during simulated weld heat affected zone in
austenitic stainless steel specimen on the stress corrosion cracking susceptibility was studied.
Residual stresses was measured using X-ray diffraction technique. Boiling Magnesium
Chloride was used as corrosive environment. Compressive stresses developed in the HAZ of
the specimen and in regions away from the HAZ stress free values were obtained. The magnitude
of the stress gradient decreased as the peak temperature attained during simulated
welding decreased. Transgranular cracks were observed in the compressive stress gradient
region and time to cracking decreased with increasing stress gradient. Higher nickel content
alloys took longer to crack as opposed to lower nickel content alloys at approximately the
same stress gradient.
Master of Science
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Kisko, A. (Anna). "Microstructure and properties of reversion treated low-Ni high-Mn austenitic stainless steels." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526212159.
Full textAbstract:
Abstract In this thesis, the influence of reversion and recrystallization annealing on microstructure and mechanical properties was studied in metastable austenitic low-Ni high-Mn stainless steels, some alloyed with up to 0.45 wt.% Nb. Further, the effect of the various microstructures created by reversion and recrystallization on strain-induced martensite transformation in tensile testing was investigated. The aim was to achieve excellent combinations of strength and ductility in the steels and to improve understanding of the behaviour of ultrafine-grained austenitic stainless steels during deformation. All the steels were cold-rolled up to 60% thickness reduction producing up to 60% strain-induced α’-martensite in the austenitic structure. Annealing was carried out using a Gleeble thermomechanical simulator between 450–1100 °C for durations of 0.1–1000 s. The resultant microstructures were examined using different research equipment and methods. Regardless of the amount of Nb alloying, shear- and diffusion-controlled reversion could be completed by annealing at 700 °C, although at this temperature no recrystallization of the untransformed cold-rolled austenite occurred. At 800 °C, however, the cold-rolled austenite recrystallized, producing a non-uniform grain structure comprising ultrafine-grained areas formed via reversion and coarser ones formed by recrystallization of the retained austenite. At 900 °C, a uniform fine austenite grain size of about 2 μm was obtained. At higher annealing temperatures of 1000–1100 °C, normal grain growth of fine grains took place during prolonged annealing in steel with no Nb. However, grain growth was effectively retarded by alloying with 0.28 wt.% Nb. The non-uniform structures consisting of reverted and retained austenite exhibited excellent combinations of yield strength and uniform elongation. The results also showed that tensile strain-induced martensite nucleation sites and α’-martensite formation vary in a complex way depending on grain sizeTiivistelmä Väitöstyössä tutkittiin reversiohehkutuksen vaikutusta metastabiilin 1% nikkeliä ja 9% mangaania sisältävien austeniittisten ruostumattomien terästen mikrorakenteeseen ja mekaanisiin ominaisuuksiin sekä austeniitin raekoon ja mikrorakenteen vaikutusta muokkausmartensiitin syntyyn vetokokeessa. Koeteräksistä osa oli lisäksi niobiseostettuja. Tavoitteena oli nostaa teräksien lujuutta ja ymmärtää ultrahienorakeisen austeniittisten ruostumattomien terästen käyttäytymistä muokkauksessa. Teräkset kylmämuokattiin 60% valssausreduktiolla, jolloin austeniittiseen rakenteeseen muodostui muokkausmartensiittia enimmillään 60%. Reversiohehkutukset tehtiin Gleeble termomekaanisella simulaattorilla lämpötiloissa 450–1100 °C ja 0.1–1000 s pitoajoilla. Saatuja mikrorakenteita tutkittiin eri tutkimuslaitteistoilla ja -menetelmillä. 700 °C hehkutuksessa leikkautumalla ja diffuusion välityksellä tapahtuva reversio oli nopea myös niobi-seostetuilla teräksillä, mutta rekristallisaatiota ei tapahtunut. 800 °C hehkutuksessa muokkauksessa teräksiin jäänyt austeniitti rekristallisoitui, mutta raerakenne muodostui epätasaiseksi koostuen reversion tuottamasta ultrahienoista rakeista ja jäännösausteniitin rekristallisaation tuottamista karkeammista rakeista. Sitä vastoin hehkutus 900 °C:ssa tuotti tasainen 2 μm austeniitin raekoon. Pitkissä hehkutuksissa korkeammissa lämpötiloissa 1000–1100 °C niobi-seostamattomissa teräksissä tapahtui hienojen rakeiden normaalia rakeenkasvua. Kuitenkin 0.28p-% niobi-seostuksen havaittiin oleva riittävä estämään rakeenkasvu. Reversion ja osittaisen rekristallisaation tuottamilla raerakenteilla saatiin erinomaiset myötölujuus-tasavenymäyhdistelmät. Vetokokeissa martensiitin ydintymispaikat ja -nopeus vaihtelivat monimutkaisella tavalla raekoosta riippuen