Journal articles: 'Dual Phase steel - DP'

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Punyamueang, Suttirat, and Vitoon Uthaisangsuk. "Determination of Stress-Strain Curve of Dual Phase Steel by Nanoindentation Technique." Key Engineering Materials 658 (July 2015): 195–201. http://dx.doi.org/10.4028/www.scientific.net/kem.658.195.

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The advanced high strength (AHS) steels, for example, dual phase (DP) steels, transformation induced plasticity (TRIP) steels and complex (CP) steels principally exhibit multiphase microstructure features. Thus, mechanical behavior of the constituent phases significantly affects the resulting overall properties of such AHS steels. Novel material characterization techniques on micro- and nano-scale have become greatly more important. In this work, stress-strain response of the DP steel grade 1000 was determined by using the Nanoindentation testing. The DP steel showed the microstructure containing finely distributed martensite islands of about 50% phase fraction in the ferritic matrix. The nano-hardness measurements were firstly performed on each individual phase of the examined steel. In parallel, finite element (FE) simulations of the corresponding nano-indentation tests were carried out. Flow curves of the single ferritic and martensitic phases were defined according to a dislocation based theory. Afterwards, the load and penetration depth curves resulted from the experiments and simulations were compared. By this manner, the proper stress-strain responses of both phases were identified and verified. Finally, the effective stress-strain curve of the investigated DP steel could be determined by using 2D representative volume element (RVE) model.

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Mohrbacher, Hardy, Jer-Ren Yang, Yu-Wen Chen, Johannes Rehrl, and Thomas Hebesberger. "Metallurgical Effects of Niobium in Dual Phase Steel." Metals 10, no. 4 (April 12, 2020): 504. http://dx.doi.org/10.3390/met10040504.

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Dual phase (DP) steels are widely applied in today’s automotive body design. The favorable combination of strength and ductility in such steels is in first place related to the share of ferrite and martensite. The pronounced work hardening behavior prevents localized thinning and allows excellent stretch forming. Niobium microalloying was originally introduced to dual phase steel for improving bendability by refining the microstructure. More recently developed “high ductility” (HD) DP steel variants provide increased drawability aided by a small share of austenite retained in the microstructure. In this variant niobium microalloying produces grain refinement and produces a dispersion of nanometer-sized carbide precipitates in the steel matrix which additionally contributes to strength. This study investigates the microstructural evolution and progress of niobium precipitation during industrial processing of high-ductility DP 980. The observations are interpreted considering the solubility and precipitation kinetics of niobium. The influences of niobium on microstructural characteristics and its contributions to strength and formability are discussed.

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Rasouli, Azam, and Mohammad Mazinani. "The Assessment of Work Hardening Behaviour of Dual Phase Steels with Coarse Martensite Islands." Advanced Materials Research 476-478 (February 2012): 311–15. http://dx.doi.org/10.4028/www.scientific.net/amr.476-478.311.

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In this paper, the tensile properties of dual phase (DP) steels with different martensite contents have been studied. Two steels with 0.09 and 0.15% carbon were used for the production of DP steel samples via intercritical annealing treatment, and the deformation behaviour of DP steel samples were examined during tensile loading. Although DP steels usually show two-stage work hardening behaviour, DP steels in this study with relatively high martensite content and coarse islands size exhibit a three-stage work hardening behaviour. This unusual behaviour was attributed, with the help of SEM micrographs, to decohesion of martensite-ferrite interface and martensite cracking.

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Abdo, Hany S., Asiful H. Seikh, Biplab Baran Mandal, Jabair A. Mohammed, Sameh A. Ragab, and Mohamed S. Abdo. "Microstructural Characterization and Corrosion-Resistance Behavior of Dual-Phase Steels Compared to Conventional Rebar." Crystals 10, no. 11 (November 23, 2020): 1068. http://dx.doi.org/10.3390/cryst10111068.

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Dual-phase (DP) steels consist of a ferritic matrix dispersed with some percentage of martensite, which gives the material a good combination of strength and ductility, along with the capacity to absorb energy and enhanced corrosion protection properties. The purpose of this work was to study the microstructural and corrosion behavior (mainly pitting and galvanic corrosion) of DP steel compared with that of conventional rebar. To obtain DP steel, low-carbon steels were heat-treated at 950 °C for 1 h and then intercritically annealed at 771 °C for 75 min, followed by quenching in ice-brine water. The corrosion rates of DP steel and standard rebar were then measured in different pore solutions. Macro- and microhardness tests were performed for both steels. It was found that DP steels exhibited a superior corrosion resistance and strength compared to standard rebar. The reported results show that DP steels are a good candidate for concrete reinforcement, especially in aggressive and corrosive environments.

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Pan, Zhiyi, Bo Gao, Qingquan Lai, Xuefei Chen, Yang Cao, Manping Liu, and Hao Zhou. "Microstructure and Mechanical Properties of a Cold-Rolled Ultrafine-Grained Dual-Phase Steel." Materials 11, no. 8 (August 10, 2018): 1399. http://dx.doi.org/10.3390/ma11081399.

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A new processing route to produce Ultrafine-Grained Dual-Phase steel has been proposed, involving cold-rolling and subsequent intercritical annealing of a fibrous ferrite–martensite starting structure. Ultrafine-grained DP (UFG-DP) steel with an average ferrite grain size of about ~2.7 μm and an average martensite island size of ~2.9 μm was achieved. Tensile testing revealed superior mechanical properties (the ultimate tensile strength of 1267 MPa and uniform elongation of 8.2%) for the new DP steel in comparison with the fibrous DP steels. The superior mechanical properties are attributed to the influence of microstructure refinement on the work-hardening and fracture behavior.

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Kuang, Shuang, Xiu Mei Qi, and Yun Han. "Analysis of Microstructures and Mechanical Properties of Two Hot Dip Galvanized Dual-Phase Steels with Different Alloy Systems." Applied Mechanics and Materials 624 (August 2014): 198–201. http://dx.doi.org/10.4028/www.scientific.net/amm.624.198.

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The microstructures and mechanical properties of a high carbon DP steel and a low carbon Nb microalloying DP steel were investigated. The two types of DP steels have both qualified to meet European standard performance. But the high carbon content DP steel exhibits relatively low elongation and low hole expansion rate as well as poor bending performance. The martensite island in high carbon DP steel appears obvious band structure, and the size of martensite islands is big. Contrary, the matensite islands in low carbon and Nb microalloying DP steel are dispersed and fine, which lead to perfect comprehensive performance.

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Wang, Zhi Gang, Zheng Zhi Zhao, Ai Min Zhao, and Jie Yun Ye. "Microstructure and Recrystallization Texture Characterization of Cold-Rolled Dual-Phase Steel." Advanced Materials Research 430-432 (January 2012): 1223–26. http://dx.doi.org/10.4028/www.scientific.net/amr.430-432.1223.

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Deep drawing dual phase steel was designed and trial-produced in the laboratory. The microstructure and recrystallization texture was studied using OM,TEM and XRD techniques. The results show that texture components typically in DP steels are γ (<111>//ND) and α (<110>//RD) fibers, which is partly attributed to the precipitation of Mo-based carbides in hot-rolled plate. Besides, {554}<225> and {332}<113> texture components are also founded in deep drawing DP steels, which are beneficial to improvement of drawability. With the increasing of annealing temperature, the tensile strength and elongation of DP steels are increased and decreased, respectively, and the r value is reduced slightly.

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Hafez, Khalid M., M. Ramadan, N. Fathy, and Mona Ismail. "Microstructure and Mechanical Properties of Laser Welded Dual Phase and Mild Steel Joints for Automotive Applications." Applied Mechanics and Materials 865 (June 2017): 81–87. http://dx.doi.org/10.4028/www.scientific.net/amm.865.81.

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Recently, the laser welding technology of carbon steel is being widely used compared with arc welding technology for its better welding characteristics. In the present study, the influence of welding conditions of both laser beam welding (LBW) and gas metal arc welding (GMAW) as a comparative study on the weld joint microstructures, hardness distribution and fatigue properties crosses the butt-welded joints of dual phase (DP) steel and mild steel are investigated. The results show that LBW produced narrow welds with complete penetration while GMAW produces wide fusion and heat affected zones. The microstructure of the fusion zone of laser welded DP steels contains mainly bainite, martensite, and a few amount of acicular ferrite phases. Hardness values of the heat-affected zone (HAZ) for dual-phase (DP) steels showing lower values for both LBW and GMAW processes due to the tempering action of the martensite phase. A narrow softening region was clearly observed in the HAZ welded for LBW compared with GMAW. In general, the fatigue life of the welded joints is improved by using laser welding technique.

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Hashimoto, Shunichi. "Effect of Niobium on Zn-Coated Dual Phase Steel Sheet." Materials Science Forum 539-543 (March 2007): 4411–16. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4411.

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Dual Phase (DP) steel sheets, mainly 590 MPa TS grade steel, have been applied to structural parts of automobile because of their good formability, large bake hardenability and high crash worthiness. Although the concept of DP steel was established as early as the mid-1970th, the literature contains little discussion of Zn-coated DP steel, which has been the main application in recent years. In manufacturing Zn-coated DP steel, chemical composition which secures adequate Zn coatability and appropriate heat cycles, including galvannealing, must be considered. In this paper, the effect of Nb on the tensile properties, stretch flange formability and bake hardenability of 590 MPa TS grade DP steel is discussed. The base chemical composition was 0.05%C-2%Mn-0.5%Cr steel. The effect of Nb on the above-mentioned properties was studied using 0.05%Nb added steel and found that the addition of 0.05%Nb results in improved elongation, stretch flangeability and bake hardenability with higher tensile strength under both simulated GA and GI heat cycles. These improved properties by the addition of Nb are brought about by the grain refinement of ferrite matrix and finer dispersion of martensite.

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Kang, Jun-Yun, Seong-Jun Park, and Man-Been Moon. "Phase Analysis on Dual-Phase Steel Using Band Slope of Electron Backscatter Diffraction Pattern." Microscopy and Microanalysis 19, S5 (August 2013): 13–16. http://dx.doi.org/10.1017/s1431927613012233.

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AbstractA quantitative and automated phase analysis of dual-phase (DP) steel using electron backscatter diffraction (EBSD) was attempted. A ferrite–martensite DP microstructure was produced by intercritical annealing and quenching. An EBSD map of the microstructure was obtained and post-processed for phase discrimination. Band slope (BS), which was a measure of pattern quality, exhibited much stronger phase contrast than another conventional one, band contrast. Owing to high sensitivity to lattice defect and little orientation dependence, BS provided handiness in finding a threshold for phase discrimination. Its grain average gave a superior result on the discrimination and volume fraction measurement of the constituent phases in the DP steel.

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Mazinani, M., and Warren J. Poole. "Deformation Behaviour of Martensite in a Low-Carbon Dual-Phase Steel." Advanced Materials Research 15-17 (February 2006): 774–79. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.774.

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The deformation behaviour of martensite and its effect on tensile properties of a lowcarbon dual-phase (DP) steel were investigated. DP steel samples with different martensite contents and morphologies were produced after intercritical annealing at different temperatures using low and high heating rates. Two distinct martensite morphologies were obtained for low and high heating rates. The investigated steel showed the unusual results that the true fracture stress and strain were found to increase with the martensite volume fraction. The plastic deformation of martensite was considered to be responsible for these results. Experimentally, it was observed that the martensite in DP steels with greater than 25-30% martensite can deform plastically during tensile straining. Finally, the effect of tempering on the martensite plasticity was also evaluated. It was found that the tempering process and an increase in the martensite content have a similar effect on promoting martensite plasticity.

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Yamanaka, Akinori. "Prediction of 3D Microstructure and Plastic Deformation Behavior in Dual-Phase Steel Using Multi-Phase Field and Crystal Plasticity FFT Methods." Key Engineering Materials 651-653 (July 2015): 570–74. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.570.

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The plastic deformation behavior of dual-phase (DP) steel is strongly affected by its underlying three-dimensional (3D) microstructural factors such as spatial distribution and morphology of ferrite and martensite phases. In this paper, we present a coupled simulation method by the multi-phase-field (MPF) model and the crystal plasticity fast Fourier transformation (CPFFT) model to investigate the 3D microstructure-dependent plastic deformation behavior of DP steel. The MPF model is employed to generate a 3D digital image of DP microstructure, which is utilized to create a 3D representative volume element (RVE). Furthermore, the CPFFT simulation of tensile deformation of DP steel is performed using the 3D RVE. Through the simulations, we demonstrate the stress and strain partitioning behaviors in DP steel depending on the 3D morphology of DP microstructure can be investigated consistently.

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Liao, Xin Sheng, Xiao Dong Wang, Xu Fei Li, Zheng Hong Guo, and Yong Hua Rong. "Design and Characterization of Ultrahigh Strength Dual-Phase Steel with Low Ratio of Yield Strength/Ultimate Tensile Strength." Advanced Materials Research 97-101 (March 2010): 728–32. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.728.

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An ultrahigh strength dual-phase (DP) steel with low ratio of yield strength/ultimate tensile strength (YS/UTS) was designed based on the simulation using JmatPro software so as to improve formability as well as to extend its application in automobile industry. Results show the DP steel suffered from water quenching (WQ) technology exhibits high ratio, 0.872, of YS/UTS, which loses the advantage of formability of DP steels and restricts its application in automobile industry. Therefore, the controlled slow-cooling rate (CSCR) technology is employed to this DP steel, and the low ratio, 0.458, of YS/UTS is obtained. Although the tensile strengths of the DP steel suffered from two kinds of technologies are over 1000 MPa, The YS of the DP steel with CSCR technology is 480 MPa and is much lower than 983MPa of the DP steel with WQ technology, which are attributed to relative large grains and small volume fraction of martensite in the former based on the characterization of microstructure by optical microscope, scanning electron microscope, transmission electron microscope and electron backscattering diffraction.

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Filep, Adám, and Valéria Mertinger. "Microstructure Characterization of Deep-Drawn DP780-Grade Dual Phase Steel." Materials Science Forum 752 (March 2013): 75–84. http://dx.doi.org/10.4028/www.scientific.net/msf.752.75.

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Dual phase (DP) steels belong to the group of high-strength low-alloy (HSLA) steels. Our study focuses on the causes of crack formation of sheets, which are designed for deep drawing, of DP780-grade dual phase steel. Also, a series of heat treatment experiments were performed regarding the effect of intercritical annealing temperature on the structure and mechanical properties of the finished product (in this case a rolled sheet).

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Xiong, Zhiping, Andrii G. Kostryzhev, Yanjun Zhao, and Elena V. Pereloma. "Microstructure Evolution during the Production of Dual Phase and Transformation Induced Plasticity Steels Using Modified Strip Casting Simulated in The Laboratory." Metals 9, no. 4 (April 16, 2019): 449. http://dx.doi.org/10.3390/met9040449.

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Instead of conventional steel making and continuous casting followed by hot and cold rolling, strip casting technology modified with the addition of a continuous annealing stage (namely, modified strip casting) is a promising short-route for producing ferrite-martensite dual-phase (DP) and multi-phase transformation-induced plasticity (TRIP) steels. However, at present, the multi-phase steels are not manufactured by the modified strip casting, due to insufficient knowledge about phase transformations occurring during in-line heat treatment. This study analysed the phase transformations, particularly the formation of ferrite, bainite and martensite and the retention of austenite, in one 0.17C-1.52Si-1.61Mn-0.195Cr (wt. %) steel subjected to the modified strip casting simulated in the laboratory. Through the adjustment of temperature and holding time, the characteristic microstructures for DP and TRIP steels have been obtained. The DP steel showed comparable tensile properties with industrial DP 590 and the TRIP steel had a lower strength but a higher ductility than those industrially produced TRIP steels. The strength could be further enhanced by the application of deformation and/or the addition of alloying elements. This study indicates that the modified strip casting technology is a promising new route to produce steels with multi-phase microstructures in the future.

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Minami, Hidekazu, Shinjiro Kaneko, Kaneharu Okuda, and Yasunobu Nagataki. "Effects of α+γ Intercritical and γ Single-Phase Annealing on Texture Evolution in Cold-Rolled Dual-Phase Steel Sheets." Materials Science Forum 879 (November 2016): 1300–1304. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1300.

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Dual-phase (DP) steel sheets composed of both soft ferritic and hard martensitic phases are typical advanced high strength steel sheets applicable to a variety of automobile parts. The crystallite texture of the steel sheet is one of the important factors that influence press formability. However, the texture of the martensite itself in DP steels has not been discussed since the texture was generally measured by the X-ray diffraction method, which does not distinguish the texture of martensite from that of ferrite. The objective of this study is to investigate the effects of intercritical and γ single-phase annealing on the texture evolution in DP steels by a newly-developed analysis method using Electron Back-Scatter Diffraction (EBSD) to obtain the texture of each phase separately. The chemical composition of the steel used was 0.1%C-1.2%Si-2.3%Mn-0.1%Ti (mass%). The 1st-annealing was carried out at 948K, which is below the Ac1 temperature, in order to finish recrystallization after hot and cold rolling so as to focus on the transformation texture evolution itself. The steels were subsequently annealed both at 1123K in the intercritical region and at 1223K in the γ single-phase region to obtain DP microstructures with approximately 40% volume fraction of martensite. The overall texture including martensite in the case of intercritical annealing was similar to the initial texture before annealing, while the texture became randomized in the case of γ single-phase annealing. Moreover, our unique EBSD analysis method clearly showed that the textures of the martensite themselves were close to those of ferrite under the two annealing conditions.

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Marvi-Mashhadi, M., A. Rezaee-Bazzaz, and Mohammad Mazinani. "Modelling the Flow Behaviour of Dual-Phase Steels with Different Martensite Volume Fractions by Finite Element Method." Materials Science Forum 706-709 (January 2012): 1503–8. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1503.

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Dual-phase (DP) steels have a composite-type microstructure consisting mainly of hard martensite islands embedded in a soft ferrite matrix. DP steels exhibit a characteristic combination of high strength, high work hardening rate and good ductility. Mechanical behaviour of DP steels is closely related to their microstructures. Hence, it is necessary to take into account their microstructural parameters in any attempt to estimate their flow behaviour. In this study, the flow curves of low carbon DP steels with 26.4 and 52% martensite produced by intercritical annealing processes at different temperatures were calculated using the finite element method (FEM). According to the results of microscopical observations of steel microstructures, martensite islands were assumed in the model to be spherical in shape. Moreover, in agreement with the experimental results in the literature clearly showing the possibility of martensite plastic deformation in similar steels during straining when its volume fraction is greater than about 30%, the plasticity of martensite islands in the steel microstructures was taken into account in the model by using their experimentally obtained stress-strain relations as a function of their estimated carbon contents. Having estimated the stress-strain behaviour of the ferrite phase in all steel samples using the microstructural parameters corresponding to the starting ferrite+pearlite steel, the flow curves of different DP steel samples with elastic martensite (in low martensite content steels) and elasto-plastic martensite (in high martensite content samples) were calculated. The calculated stress-strain curves exhibited reasonable agreements with the experimental stress-strain curves obtained from the tensile tests.

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Šebek, Martin, Peter Horňak, Svätoboj Longauer, Peter Zimovčák, and Pavol Zahumenský. "Relationship of Microstructure and Mechanical Properties of Dual Phase Steel after Various Annealing Conditions." Materials Science Forum 891 (March 2017): 176–81. http://dx.doi.org/10.4028/www.scientific.net/msf.891.176.

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The development of ultrafine ferrite grain size has become one of attractive way how to improve the behavior of dual phase (DP) steels. The other possible way how to enhance mechanical properties of DP steels is to modify the chemical composition. Therefore object of our investigation was the dual phase steel with modified alloying (three times higher Cr content with addition of phosphorus). The dual phase steel was annealed in laboratory conditions in accordance with three specified annealing cycles: into intercritical region (780°C), into austenite region (920°C) and into austenite region (920°C) by subsequently cooling into intercritical region (780°C) with the hold at the temperature of 495°C. The obtained microstructure after selected annealing regimes consists of three phases (ferritic matrix, martensite and martensite/bainite grains) with different size and distribution. For studied annealing regimes were clearly defined mechanical properties such as: YS, UTS, elongation, n-parameter and ratio YS/UTS. It was defined the scheme of microstructure evolution on base of austenite grain size during the continual cooling process with defined three phases: 1) the hard martensite formed on the grain boundary; 2) the soft interior bainite and 3) the hard isolated martensite.

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Pushkareva, Irina, Abdelkrim Redjaïmia, Antoine Moulin, and Nathalie Valle. "A Study of Dual Phase Steel Damage Evolution with Microstructure." Solid State Phenomena 172-174 (June 2011): 839–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.839.

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A detailed analysis of the evolution of industrial Dual Phase (DP) steel microstructures is carried out as a function of various annealing and tempering conditions. Advanced characterization techniques such as Parallel Electron Energy Loss Spectroscopy (PEELS) in the TEM and high spatial resolution Secondary Ion Mass Spectrometry (NanoSIMS) are employed in order to provide qualitative and quantitative measurements of local carbon concentration in the martensite. For certain annealing and tempering conditions, it is observed that local variations in carbon levels have occurred inside the individual martensite islands. These carbon variations strongly influence the damage behaviour of the steel. During tensile tests, a clear dependence of the damage mode on the local martensite carbon content is observed. Better knowledge of the relationship between the microstructure evolution at the sub-grain level and the damage behaviour can facilitate the design of DP steels with improved damage resistance.

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Li, Guo Bin, Zheng Zhi Zhao, and Di Tang. "Microstructure Evolution and Mechanical Properties of 780 MPa Hot Dip Galvanized Dual-Phase Steel." Advanced Materials Research 146-147 (October 2010): 1331–35. http://dx.doi.org/10.4028/www.scientific.net/amr.146-147.1331.

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The microstructure evolution of 780 MPa hot dip galvanized dual-phase (DP) steel at heating stages of the annealing process was analyzed using a Gleeble−3500 thermal/mechanical simulator. A multifunction continuous annealing simulator was employed to investigate the effect of annealing process on microstructure and mechanical properties of hot dip galvanized DP steel. The experimental results show that ferrite recovery and recrystallization, pearlite dissolution and austenite nucleation and growth take place in the annealing process of hot dip galvanized DP steel. The hardenability can be significantly improved by trace addition of vanadium. When the soaking temperature reaches 780 °C, the tensile strength and total elongation of DP steel can reach 785MPa and 15%, respectively. The microstructure of DP steel mainly consists of a mixture of ferrite and martensite.

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Lv, Wei, Di Wu, and Zhuang Li. "Thermo-Mechanical Simulation of Ultra-High Strength Ferrite-Bainite Dual Phase Steel." Applied Mechanics and Materials 184-185 (June 2012): 1367–70. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.1367.

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In the present paper, thermo-mechanical simulation of ultra-high strength ferrite-bainite dual phase (DP) steel was performed using a thermomechanical simulator. Continuous cooling transformation (CCT) diagram was constructed for DP steel. The effects of composition and cooling rate on the kinetics and products of phase transformation and the form of the CCT diagram were investigated. The results have shown that the α→γ transformation in DP steel was found to be more sluggish due to the addition of alloying elements. The segregation of manganese and niobium at austenite grain boundaries is expected to cause a solute drag effect, thereby reducing the rate of γ→α transformation in DP steel. The pearlite transformation region disappeared for cooling rates from 0.1 to 20°C/s. The microstructure comprises of bainite and martenite was obtained at fast cooling rate. The present steel is expected to have a higher hardenability.

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Zhang, Chun Ling, Da Yong Cai, Ke Qin Zhang, and Bo Liao. "Effect of Dual-Phase Treatment on the Corrosion Behavior of Weathering Steel 09CuPCrNi." Advanced Materials Research 740 (August 2013): 586–90. http://dx.doi.org/10.4028/www.scientific.net/amr.740.586.

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Dual-phase steels of 09CuPCrNi are prepared through intercritical quenching process. The influences of dual-phase treatment on the corrosion resistant property of the steels have been studied by electrochemical potentiodynamic tests and artificial salt spray tests. The results indicate that the corrosion behavior of DP780 and the as-received weathering steel in 5% sodium hydroxide, 3.5% sodium chloride, 5% sulphuric acid and various concentrations of hydrochloric acid solutions are identical, but dual-phase steels show least corrosion current as compared to the as-received steel. Rust layers of the as-received steel and DP780 are identical mainly consisting of three iron (hydr) oxides, goethite, akaganeite and lepidocrocite, and magnetite. Both the relative amount and morphology of phase constituents affect on the corrosion behavior of DP steels.

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Basoeki, Prita Dewi. "Effects of DP steel microstructure on the disappearance of discontinuous yielding." MATEC Web of Conferences 204 (2018): 07013. http://dx.doi.org/10.1051/matecconf/201820407013.

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Although in terms of quality is not as high as TRIP steel, DP steel has been developed as an option to meet the minimum standard industrial requirement for automotive. Steel development for automotive material leads to posses high strength without suffering its ductility and weld ability, in addition there is no appearance of discontinuous yielding that cause stretcher strain marking. The change of micro structure as a result of the intercritical annealing process not only increases the strength of Dual Phase Steel, but also eliminates the discontinuous yielding. The phenomenon of discontinuous yielding is no longer appear in Dual Phase Steel which heating time on intercritical annealing process more than 1 minute, the minimum time is equal to the disappearance of discontinuous yielding. The phenomenon of upper yield point and discontinuous yielding on carbon steel is strongly influenced by the magnitude of the stress acting on the Ferrite phase to move the dislocation of the pinned state by the interstitial atom. From the recent works gives the result that the disappearance of discontinuous yielding in Dual Phase Steel resulting from the intercritical annealing process makes Dual Phase Steel very suitable as an automotive material.

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Tian, Chunhua, and Christoph Kirchlechner. "The fracture toughness of martensite islands in dual-phase DP800 steel." Journal of Materials Research 36, no. 12 (March 17, 2021): 2495–504. http://dx.doi.org/10.1557/s43578-021-00150-4.

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Abstract In situ microcantilever bending tests were performed on martensite islands in a dual-phase (DP) steel to extract the fracture toughness of martensite at the microscale and to understand damage initiation during forming of DP steels. All microcantilevers were produced through FIB milling. The martensite islands do not exhibit linear elastic brittle fracture; instead, significant ductile tearing is observed. The conditional fracture initiation toughness extracted by definition and by Pippan’s transfer criterion is Ki = 6.5 ± 0.4 MPa m1/2 and Ki,2% = 10.1 ± 0.3 MPa m1/2, respectively. The obtained value is well-represented by the strength-toughness trend of other ferritic steel grades. Considering the yield stress of the same martensite island, we found that crack initiation can occur only in very large martensite islands or in a banded or agglomerated martensite structure. Graphic abstract

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Lian, Jun He, Napat Vajragupta, and Sebastian Münstermann. "Micromechanical Modeling of Damage and Failure in Dual Phase Steels." Key Engineering Materials 554-557 (June 2013): 2369–74. http://dx.doi.org/10.4028/www.scientific.net/kem.554-557.2369.

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Dual phase (DP) steels consisting of two phases, ferrite and dispersed martensite, offer an attractive combination of strength and stretchability, which is a result of the strong distinctions of these constituents in mechanical properties. However, the damage behavior in DP steels exhibits a rather complex scenario: voids are generated by the debonding of the hard phase from the matrix and the inner cracking of the hard phase in addition to by inclusions. The target of this study is to describe the initiation and evolution of damage in DP steel and develop a microstructure-based model which is capable of reflecting the underlying damage mechanisms. Both uniaxial and biaxial tensile tests are performed and the subsequent metallographic investigations are executed to reveal the mechanisms of damage initiation and evolution under different stress state condition and attention will be paid on the influence of various microstructural features on the initiation of damage. In finite element (FE) simulations, the microstructural features are taken into account by the representative volume elements (RVE). Different treatments of the constitutive behaviour of each constituent including isotropic hardening rule and crystallographically dependent configuration with crystal plasticity finite element method are investigated. Several numerical aspects are also discussed, such as RVE size, mesh size, element type, and boundary connections. In the end, the study is attempting to achieve a quantitative assessment of the cold formability of the investigated steel in a microscopic level based on microstructure information of material as well as to understand the damage mechanisms under different stress states condition which cause the macroscopic failure during plastic deformation.

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Ramazani, Ali, Alexander Schwedt, Anke Aretz, and Ulrich Prahl. "Failure Initiation in Dual-Phase Steel." Key Engineering Materials 586 (September 2013): 67–71. http://dx.doi.org/10.4028/www.scientific.net/kem.586.67.

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This research work aims to model the failure initiation in dual-phase (DP) steel. A microstructure based approach by means of representative volume elements (RVE) is employed to evaluate the microstructure deformation and the failure initiation on the mesoscale. In order to determine cohesive parameters for martensite cracking, a two level approach has been performed experimentally. First, in-situ bending test in SEM with EBSD measurements before and after the test showed that the crack initiation occurs in martensite islands. Then, mini tensile tests with DIC technique were carried out to identify macroscopic failure initiation strain values. RVE modeling combined with extended finite element method (XFEM) was utilized to model martensite cracking on mesoscale. The identified parameters were validated by comparing the predictions with the experimental results.

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Chen, Chih Yuan, Cheng Han Li, Pei Herng Liu, Shao Pu Tsai, Chien Chon Chen, and Jer Ren Yang. "Precipitation Characterization and Mechanical Behavior in Novel DP Steels." Materials Science Forum 939 (November 2018): 9–15. http://dx.doi.org/10.4028/www.scientific.net/msf.939.9.

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Dual precipitates of carbide and copper particles formed within Cu-Ti microalloyed DP (Dual Phase) steel in the present study. The precipitation behaviors of tiny precipitates, especially in the ferrite matrix, were checked precisely by several methods, such as optical microscopy, high resolution transmission electron microscopy, and hardness testing. It was found that copper particles nucleated only on the interphase precipitated TiC and were not dispersed randomly within the ferrite matrix. Therefore, the formation of dual precipitates within the ferrite grains should be considered as separated phase transformation; initially, only titanium carbides form during the austenite decomposition reaction, after which copper particles heterogeneously nucleate on these carbides. Furthermore, as compared to Cu microalloyed DP steel, the tempering behavior of martensite in the Cu-Ti microalloyed DP steel showed a tempering hardening characteristic.

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Zhao, Kun, Xin Cun Zhuang, Xin Hua Pei, and Zhen Zhao. "Influence of Geometrical Imperfection on Failure Mode of DP780 Steel Utilizing Damage Models Embedded RVE Technique." Key Engineering Materials 725 (December 2016): 471–76. http://dx.doi.org/10.4028/www.scientific.net/kem.725.471.

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As dual-phase (DP) steel sheet is widely used in automotive manufacture, researches on failure mode of DP steel have been carried out experimentally and numerically in recent years. In this paper, failure mode of DP 780 steels with geometrical imperfection, which was assumed as a consequence of previous process, was investigated via a microstructure approach utilizing RVE technique. Multiple damage models were applied on characteristic microstructures and the modified pointed-ended geometrical imperfection was ingrained. Considering the progress of crack evolution, the depth and the location of geometrical imperfection were critical factors in determining the mode of crack initiation and propagation. Essentially, geometrical imperfection influenced the failure mode of investigated DP steel via aggravating the structural heterogeneity.

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Lv, Wei, Di Wu, and Zhuang Li. "Development of Laminar Flow Cooling of Ultra-High Strength Ferrite-Bainite Dual Phase Steel." Applied Mechanics and Materials 184-185 (June 2012): 940–43. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.940.

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In the present paper, controlled cooling in different ways was performed using a laboratory hot rolling mill in ultra-high strength hot rolled ferrite-bainite dual phase (DP) steel. The results have shown that the final microstructures of DP steel comprise ferrite, bainite and a small amount of retained austenite and martensite. DP steel has a tensile strength ranging from 1010 to 1130MPa and yet retains considerable total elongation in the range of 14–17%. The addition of Mn and Nb to DP steel leads to the maximum ultimate tensile strength, yield strength and the product of ultimate tensile strength and total elongation due to the formation of retained austenite and granular bainite structure. Laminar flow cooling after hot rolling results in a significant increase in the quantity of ferrite and bainite due to the suppression of pearlite transformation, and as a result, the present steel possesses high strengths and good toughness.

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30

Janssen, M. H. E., M. J. M. Hermans, M. Janssen, and I. M. Richardson. "Fatigue Performance of Laser Brazes in Advanced High Strength Steels." Materials Science Forum 638-642 (January 2010): 3254–59. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3254.

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Advance high strength steels (AHSS), like dual phase (DP) and transformation induced plasticity (TRIP) steels, offer high strength and toughness combined with excellent uniform elongation. However, the higher alloying content of these steels limit their weldability and the thermal cycle of welding processes destroys the carefully designed microstructure. This will result in inferior mechanical properties of the joint. Therefore, joining processes with a low heat input, like brazing, are recommendable. Data regarding mechanical properties of joints in DP and TRIP steel is limited, especially for brazed joints. Results with respect to the fatigue lifetime of laser brazed butt joints are presented. In DP and TRIP steel, crack initiation takes place at the braze toe. In DP steel the crack propagates through the base metal. In TRIP steel, however, the crack may either follow the interface or may continue through the steel depending on the maximum stress level. The different failure mechanisms are explained on the basis of process conditions, the microstructure and the stress state.

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31

Yamanaka, Akinori, and Tomohiro Takaki. "Simulation of Microstructure Evolution and Deformation Behavior for Dual-Phase Steel by Multi-Phase-Field Method and Elastoplastic Finite Element Method." International Journal of Automation Technology 7, no. 1 (January 5, 2013): 16–23. http://dx.doi.org/10.20965/ijat.2013.p0016.

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A coupled simulation method is developed by using a Multi-Phase-Field (MPF) method that is recognized as a powerful numerical method for simulating microstructure formation in material and ElastoPlastic Finite Element Analysis (EP-FEA) based on a homogenization method. We apply the developed simulation method to investigate the deformation behavior of DP steel that includes various volume fractions and morphologies of the ferrite (α) phase. To obtain morphological information on the α phase of DP steel, we performed MPF simulation of austenite-to-ferrite (γ → α) transformation during continuous cooling transformation. MPF simulation gives us the digital image of the distribution of the simulated α phase. Furthermore, we model the representative volume element, which describes the DP microstructure, on the basis of the obtained morphology of the α phase, and perform tension-compression testing of DP steel, including the simulated α phase. Through these simulations, it is confirmed that the developed simulation method enables us to clarify the effect of the volume fraction and the configuration of the α phase on macroscopic deformation behavior of DP steel, such as the Bauschinger effect.

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32

Hocine, Tassi, Zidelmel Sami, and Allaoui Omar. "Effect of Martensite Morphologies on Corrosion in 5% H2SO4 Solution of Borided X70 Dual Phase Steel." Annales de Chimie - Science des Matériaux 45, no. 1 (February 28, 2021): 69–74. http://dx.doi.org/10.18280/acsm.450109.

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In the present investigation, some electrochemical properties of dual phase X70 steels with different martensite morphologies which have undergone boriding were studied. To obtain a variety of martensite morphologies, Direct Quenching (DQ), Intermediate Quenching (IQ) and Step Quenching (SQ) heat treatments were applied at an intercritical annealing temperature (IAT) of 760℃. The treatment (DQ) allowed the formation of fine martensite evenly distributed in the ferrite matrix. (IQ) treatment showed the formation of martensite along the ferrite / ferrite grain boundaries. In contrast, treatment (SQ) induced the formation of a banded morphology of martensite and ferrite. The realization of borides on X70 (DP) steel was carried out in a powder mixture containing 5% of B4C as source of boron, 5% of NaBF4 as activator and 90% of SiC as diluent at 950℃ for a period of time from 4 h. The corrosion behavior of X70 (DP) steel has been explored by the Tafel extrapolation method in a 5 wt. % H2SO4 solution. The corrosion resistance of steel which has undergone boriding (BDP) is higher than that of steel which has not undergone it (DP).

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33

Xu, Xiang Jun, and Jun Qi Kong. "Study on Cooling Process of Hot Rolled Wire Rod with Dual Phase Microstructure." Advanced Materials Research 415-417 (December 2011): 779–83. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.779.

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In the present paper effect of post deformation cooling rates on microstructure of ER70S-6 steel was investigated by using Gleeble1500 simulator. From the results, a controlling cooling process for obtaining dual phase (DP) microstructure was designed to produce hot rolled wire rod with a diameter of 6.5mm in a continuous no-twist and high-speed wire rolling mill, and the microstructures and the tensile properties of the wire rod were analyzed. The results showed that ER70S-6 steel deformed at 845°C and cooled at a rate of faster than 10°C/s had a DP microstructure with grain size of less than 8.3μm and martensitic volume fraction of 9-11%. The hot rolled wire rod cooled by blowing air had a DP microstructure with a grain size of 8.2μm and martensitic volume fraction of 11.5%. The present wire rod was superior to that of the same steel with ferrite plus pearlite microstructure in tensile properties, with yield strength level of 335-345MPa, ultimate tensile strength level of 600-620MPa, plastic elongation of 26.5-31.5% and strain hardening exponent of 0.221, respectively. ER70S-6 steel wire rod with DP microstructure showed promise of meeting the requirements for grade 8.8 fastener.,In the present paper steel wire rod with DP microstructure showed promise of meeting the requirements for grade 8.8 fastener.

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34

Shen, Jie, Yan Song Zhang, and Xin Min Lai. "Effect of Electrode Force on Expulsion in Resistance Spot Welding with Initial Gap." Materials Science Forum 675-677 (February 2011): 795–98. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.795.

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Compared with the conventional low carbon steels, the expulsion is more prone to occur in resistance spot welding (RSW) of dual phase (DP) steels. Especially when the initial gap exists between the steel sheets, the weld expulsion would reduce the weld quality of the joint. It is important to decrease or inhibit the occurrence of the weld expulsion in auto-body assembly line in order to guarantee the joint quality. In this study, the experiments of RSW with different initial gaps have been done to study the effect of the electrode force on the expulsion using different thicknesses of dual phase steels. The results show that the increment of the electrode fore would enable to decrease the occurrence of expulsion with the increase of the sheet thickness and gap spacing in resistance spot welding of DP steel sheets.

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35

Krebs, Benoit, Alain Hazotte, Lionel Germain, and Mohamed Gouné. "QUANTITATIVE ANALYSIS OF BANDED STRUCTURES IN DUAL-PHASE STEELS." Image Analysis & Stereology 29, no. 2 (May 3, 2011): 85. http://dx.doi.org/10.5566/ias.v29.p85-90.

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Dual-Phase (DP) steels are composed of martensite islands dispersed in a ductile ferrite matrix, which provides a good balance between strength and ductility. Current processing conditions (continuous casting followed by hot and cold rolling) generate 'banded structures' i.e., irregular, parallel and alternating bands of ferrite and martensite, which are detrimental to mechanical properties and especially for in-use properties. We present an original and simple method to quantify the intensity and wavelength of these bands. This method, based on the analysis of covariance function of binary images, is firstly tested on model images. It is compared with ASTM E-1268 standard and appears to be more robust. Then it is applied on real DP steel microstructures and proves to be sufficiently sensitive to discriminate samples resulting from different thermo-mechanical routes.

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36

Kucukomeroglu, T., and S. M. Aktarer. "Microstructure, microhardness and tensile properties of FSWed DP 800 steel." Journal of Achievements in Materials and Manufacturing Engineering 2, no. 81 (April 1, 2017): 56–60. http://dx.doi.org/10.5604/01.3001.0010.2038.

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Purpose: Dual phase (DP) steels are widely used in the automotive industry due to their properties of a high balance of strength and formability. However, it is known that conventional welding of high strength steel leads to some undesirable results such as hardness decrease in the heat affected zone. Friction stir welding (FSW) is a new solid state joining method, which is used to join these steels due to its advantage of low heat input. The aim of this study is to evaluate the microstructural change and mechanical properties of friction stir welded DP800 steel. Design/methodology/approach: DP 800 steels with 1.5 mm thickness were subjected to friction stir welding, by using a tungsten carbide (WC) tool. The tool was tilted 2°, and downforce of the tool was kept constant at 6 kN. During processing, the tool rotation and traverse speed were fixed at 1600 rpm and 170 mm∙min-1, respectively. Findings: The friction stir welded region comprises martensite, bainite, refined ferrite. The average microhardness of stir zone has increased from 260 HV0.2 to about 450 HV0.2. The tensile sample shows a decrease in the ultimate tensile strength (σUTS) about 3%, from 827 MPa to 806 MPa for the joint. The yield strength (YS) of the joint is about 566 MPa and the value is near that of DP800. Research limitations/implications: The tungsten carbide tool used for the friction stir welding has suffered deterioration in the pin profile after 1 meter welding operation. It may be advisable to drill a pre-hole in the specimens for a longer tool life. Practical implications: Tool wear for industrial applications will be a major problem. Therefore, the use of tools with high wear resistance such as polycrystalline cubic boron nitride may be recommended. Originality/value: Works on friction stir welding of dual phase steels are limited and they mostly focus on spot welding. Also, this study systematically investigates the microstructure and mechanical properties of dual-phase 800 steels after the friction stir welding.

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37

Guo, Jia, Guo Sen Zhu, Zhi Qiang Yao, Jie Liu, Yu Du, and Fei Li. "Effects of the Morphology and Distribution of Ferrite and Martensite on Mechanical Properties of Dual-Phases Steel." Advanced Materials Research 631-632 (January 2013): 404–11. http://dx.doi.org/10.4028/www.scientific.net/amr.631-632.404.

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The ingots were rolled by 550 mills in laboratory to obtain dual-phase steels. The influence of the morphology and distribution of ferrite and martensite on mechanical properties of dual-phase steel was investigated. The results indicated that some amount of acicular ferrite transformed in DP steel is available for decreasing the size and homogenizing the distribution of martensite in ferrite base. Meanwhile, the values of yield strength, tensile strength and impact toughness increases apparently, the value of elongation decreases to 22.5% .

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38

Costa, Altamirano, Salinas, González-González, and Goodwin. "Optimization of the Continuous Galvanizing Heat Treatment Process in Ultra-High Strength Dual Phase Steels Using a Multivariate Model." Metals 9, no. 6 (June 21, 2019): 703. http://dx.doi.org/10.3390/met9060703.

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The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (tIA and TIA), cooling rate (CR1) after intercritical austenitizing, holding time at the galvanizing temperature (tG) and finally the cooling rate (CR2) to room temperature. In this research work, the effects of CR1, tG and CR2 on the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of cold rolled low carbon steel were investigated by applying an experimental central composite design and a multivariate regression model. A multi-objective optimization and the Pareto Front were used for the optimization of the continuous galvanizing heat treatments. Typical thermal cycles applied for the production of continuous galvanized AHSS-DP strips were simulated in a quenching dilatometer using miniature tensile specimens. The experimental results of UTS, YS and EL were used to fit the multivariate regression model for the prediction of these mechanical properties from the processing parameters (CR1, tG and CR2). In general, the results show that the proposed multivariate model correctly predicts the mechanical properties of UTS, YS and %EL for DP steels processed under continuous galvanizing conditions. Furthermore, it is demonstrated that the phase transformations that take place during the optimized tG (galvanizing time) play a dominant role in determining the values of the mechanical properties of the DP steel. The production of hot-dip galvanized DP steels with a minimum tensile strength of 1100 MPa is possible by applying the proposed methodology. The results provide important scientific and technological knowledge about the annealing/galvanizing thermal cycle effects on the microstructure and mechanical properties of DP steels.

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39

Abdo, Hany S., Asiful H. Seikh, Jabair A. Mohammed, Monis Luqman, Sameh A. Ragab, and Saud M. Almotairy. "Influence of Chloride Ions on Electrochemical Corrosion Behavior of Dual-Phase Steel over Conventional Rebar in Pore Solution." Applied Sciences 10, no. 13 (June 30, 2020): 4568. http://dx.doi.org/10.3390/app10134568.

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Reinforced steel bars (rebar) are extensively used in construction, and the main challenge is in minimizing corrosion due to oxide or passive layer breakdown. In contrast, dual-phase (DP) steel has good corrosion resistance. This study investigated the effect of Cl− ions on the electrochemical corrosion behavior of DP rebar and conventional rebar. Corrosion behavior studies and electrochemical measurements were conducted on DP rebar and conventional rebar in simulated concrete pore solution with different concentrations of Cl− ions. Microstructure analysis, surface morphology analysis, and corroded surface characterization were performed using optical microscopy, field emission scanning electron microscopy, and Raman spectroscopy, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements revealed that DP rebar has good passivity, leading to better corrosion resistance and greater strength compared to ordinary rebar. In addition, DP rebar showed better passivity behavior compared to conventional rebar in alkaline solution. Therefore, the presence of a dual phase (ferrite and martensite) in reinforced concrete structured steel induces good corrosion resistance.

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40

Meng, Jin, Ping Zhu, and Zhi Gang Hu. "Experimental Research of Prestrain Effects on Mechanical Behavior of Dual Phase Steel." Advanced Materials Research 139-141 (October 2010): 205–9. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.205.

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Dual phase (DP) steel is increasingly utilized in automotive industry to match the requirement of both performance and lightweight of autobody for economical and ecological considerations. Most of autobody structures are manufactured by stamping process which imports prestrain effects into original material and alters its static and cyclic mechanical behaviors. In this study, mechanical behavior of prestrained DP steel was researched. Firstly, microstructure of commercial DP steel with different prestrain levels was examined with optical microscope of 500X magnification. Then, static tensile experiments and strain-controlled fatigue experiments were carried out at room temperature. Test results of differenet prestrain levels were compared. Static stress-strain relationship and local strain-life model were determined using linear regression method. Furthermore, fatigue performance and notch fatigue resistance capability were compared with prestrain level based on Neuber factor. Finally, explanation of the change with prestrain was presented with crack closure theory.

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41

Xu, Yongsheng, Wenjiao Dan, Chuang Ren, Tingting Huang, and Weigang Zhang. "Study of the Mechanical Behavior of Dual-Phase Steel Based on Crystal Plasticity Modeling Considering Strain Partitioning." Metals 8, no. 10 (September 29, 2018): 782. http://dx.doi.org/10.3390/met8100782.

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The similar crystal structures of martensite (BCT) and ferrite (BCC) cause difficulty in distinguishing the grain orientations of individual phases in dual-phase (DP) steels. A dislocation-based multiphase mixed hardening model is presented, considering both ferrite and martensite strain partitioning, to describe the texture-dependent mechanical behavior of DP steels more precisely. This model is based on the ideals that (i) the volume fractions of the constituent phases and the corresponding strain partitioning function are obtained through in situ tensile experimentation, and (ii) the grain orientations of ferrite and martensite are assumed to be in accordance with the overall texture. We applied the model to calculate the macroscopic and microscopic mechanical behavior of DP800 steel using a crystal plasticity finite element (CPFE) code. The results show that the calculated stress-strain response and textural evolution are in good agreement with the experimental results. The dislocation evolution indicates that the rapid hardening of ferrite induces a high hardening rate for DP steels early in plastic deformation. In addition, for the grains corresponding to the texture center orientations of DP800, the activity and dislocation density evolutions of the slip systems are studied.

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42

Mallick, Dwaipayan, Nicolas Mary, V. S. Raja, and Bernard Normand. "Study of Diffusible Behavior of Hydrogen in First Generation Advanced High Strength Steels." Metals 11, no. 5 (May 11, 2021): 782. http://dx.doi.org/10.3390/met11050782.

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This study deals with microstructural influence on the H permeation behavior of Dual-Phase (DP) and Complex Phase (CP) steels using electrochemical permeation studies. The H diffusion coefficients in DP steels (DP800: 1.65 × 10−10 m2·s−1, DP1000: 1.58 × 10−10 m2·s−1) are half of that found in CP steels (3.07 × 10−10 m2·s−1).The banded microstructure along the specimen thickness and higher C content of the DP led to high H diffusivity of DP steels. The lower total H concentration along with a higher fraction of H was present in the stronger traps in CP steels suggest a better HE resistance of this steel. The H distribution in the specimens was non-uniform, with a higher H concentration speculated near the charging surface.

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43

Arribas, Maribel, Radhakanta Rana, Chris Lahaije, Xabier Gómez, Iñigo Aranguren, and Iñaki Pérez. "Design and Properties of 1000 MPa Strength Level Hot-Formed Steels Possessing Dual-Phase and Complex-Phase Microstructures." Materials Science Forum 941 (December 2018): 352–57. http://dx.doi.org/10.4028/www.scientific.net/msf.941.352.

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In cold forming for automotive lightweight design, advanced high strength steels (AHSS) lead to limited formability, high springback and press forces, low stretch flangeability, multiple operations for complex geometries and large scrap rates. Two sets of AHSS, namely ferritic-martensitic dual-phase (DP) steel and martensitic-bainitic complex-phase (CP) steel with some amounts of retained austenite (RA), were designed for the hot-forming route, which eliminates the above drawbacks and guarantees higher performance in the body-in-white (BIW). Design of four DP and four CP alloys was accomplished using JMatPro6.0 thermodynamic software and available literature. The alloys were manufactured in the laboratory in cold-rolled gauge of ~1.5 mm and subjected to hot-forming cycles including hot deformation (up to 20% strain), using a dilatometer and a Gleeble 3800 machine. The thermal cycles of the DP alloys included an intercritical reheating whereas in-situ austempering or slow continuous cooling followed by supercritical reheating was used for the CP alloys. The results showed that yield strength (YS) of 605MPa & 695MPa, ultimate tensile strength (UTS) of 1097MPa & 1242MPa with a total elongation (TE) of 12.6% & 14.1% can be achieved in the best performing DP alloys with a martensite content of 65% & 60 vol.%. The best CP alloys with austempering achieved YS of 673MPa & 699MPa, UTS of 983MPa & 1026MPa and TE of 9.2% & 13.6% with RA of 4%-12 vol.%. The continuously-cooled alloys achieved even better properties. Higher bendability at 1.0 mm gauge in the critical direction was achieved in the CP alloys (90o&107o) than in the DP alloys (73o&76o).

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44

Miernik, K., and S. Pytel. "Microstructure and Mechanical Properties of Dual-Phase Steel/ Mikrostruktura I Własności Mechaniczne Stali Dwufazowej." Archives of Metallurgy and Materials 59, no. 4 (December 1, 2014): 1257–61. http://dx.doi.org/10.2478/amm-2014-0215.

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Abstract The paper presents results of microstructure and mechanical properties of the dual phase (DP) steel plate with 12 mm thickness produced by intercritical annealing at a two-phase region of ferrite and austenite (α + γ) and direct quenching in water. In addition the tempering treatment at temperature of 650°C was applied to investigate effect of martensite softening on mechanical properties of the tested steel. The parameters of heat treatment were designed to achieve the high strength while retaining optimum impact strength of the DP steel.

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Djuric, Aleksija, Dragan Milčić, Damjan Klobčar, and Biljana Marković. "MULTI-OBJECTIVE OPTIMIZATION OF THE RESISTANCE SPOT-WELDING PROCESS PARAMETERS FOR THE WELDING OF DUAL-PHASE STEEL DP500." Materiali in tehnologije 55, no. 2 (April 15, 2021): 201–6. http://dx.doi.org/10.17222/mit.2020.095.

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Resistance spot welding (RSW) is still the most used form of welding in the automotive industry, primarily for welding steel. One of the advanced steels used in the automotive industry is dual-phase steel, so it is important to properly select the welding parameter for these steels. Therefore, this paper presents multi-objective optimization in the RSW welding process of DP 500 steel. The paper considers three different mechanical characteristics i.e., the failure load (F), failure displacement (l) and weld nugget diameter (D), as all these welding characteristics play significant roles in evaluating the quality of spot welding. The results show that the welding current is the most influential parameter with respect to the mechanical characteristics. The effect of welding time on the weld quality is the least significant. The optimal parameters for welding DP 500 steel obtained in this paper are weld current 8 kA, electrode force 4.91 kN and weld time 400 ms.

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46

Barbatti, Carla, Patricia Romano Triguero, Stefan Van Bohemen, Steven Celotto, and Dave N. Hanlon. "Study of Recrystallization and Phase Transformation in a Cold-Rolled Dual-Phase Steel: Influence of Temperature and Heating Rate during First Annealing Stages." Materials Science Forum 702-703 (December 2011): 818–21. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.818.

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The effect of heating path and heating rate on the microstructure and texture development in cold-rolled continuously annealed DP steel was studied by SEM and EBSD. A methodology to separate the individual phases present in mixed microstructures, and thus to enable quantification of the individual contributions to the bulk texture has been applied. It was observed that a higher heating rate may promote strengthening of {111} textures in DP steels as observed in low carbon grades.

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47

Wagih, M., M. Shahtout, and A. Kady. "Modeling of C-Mn Chromium Containing Steel to Produce DP600 through Thin Slab Direct Rolling." Materials Science Forum 638-642 (January 2010): 3502–7. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.3502.

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The design of new steel grades and microstructures is mostly motivated by the necessity of steel industry to process always better suited high strength steel with low production costs. Automotive customers are asking for more steel options to meet increased specifications for strength, crash worthiness, energy absorption, part complexity, and dent resistance. To meet these requirements, new developed types of steel known as Advanced High-Strength Steels (AHSS) were introduced (e.g.: DP steel "Dual Phase", TRIP steel "Transformation Induced Plasticity",…etc). This paper presents a case study for producing DP600 dual phase steel in EZDK company through building up an integrated model to predicting both final austenite grain size after finishing rolling and the final ferrite grain size after cooling.

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Kuang, Shuang, and Xiu Mei Qi. "High Silicon Addition in 780 MPa Cold-Rolled Dual Phase Steel for Carbon Reduction and Plastic Reinforce." Advanced Materials Research 1004-1005 (August 2014): 183–87. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.183.

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Two types of DP steels which contain high carbon and high silicon respectively were produced on industrial production line. The microstructures and mechanical properties were investigated. Based on the thermodynamics and kinetic analyses, the intercritical austenization was researched. The results show that the high silicon and low carbon composition used to DP steel can avoid martensite band structure and decrease the martensite fraction, which will improve the elongation and work hardening ability. Phase transformation kinetic analysis indicates that high silicon content can make manganese enrich in austenite and stabilize austenite in intercritical region. Assisted by the strengthening role of silicon in austenite, the mechanical properties of high silicon and low carbon DP can fully meet the standard.

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49

Nakada, Nobuo, Yusuke Arakawa, Kyo Sun Park, Toshihiro Tsuchiyama, and Setsuo Takaki. "Microstructural Control of Dual Phase Structure Formed by Partial Reversion from Cold-Deformed Martensite." Materials Science Forum 753 (March 2013): 191–94. http://dx.doi.org/10.4028/www.scientific.net/msf.753.191.

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Dual phase (DP) structure formed by partial reversion from cold-deformed martensite was investigated to improve mechanical property of DP steel by grain refinement strengthening. A low carbon martensitic steel (0.15C-1.0Mn) was cold-rolled and then held just above A1 temperature to partially form austenite. In particular, the conditions of cold-rolling rate (0~60% reduction in thickness) and heating rate (0.083 and 100 K/s) were varied to understand their effects on the microstructural development of DP structure. Although the recrystallization has never occurred in undeformed martensite, cold-deformed martensite was more easily recrystallized before reversion with increasing rolling rate and lowering heating rate. Then, the matrix of DP structure was changed from tempered martensite to recrystallized ferrite, which had a large influence on the distribution of fresh martensite transformed from reversed austenite. The higher rolling and heating rates resulted in the finer DP structure, leading to a large improvement in strength level.

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Liu, Qinglong, Qingjun Zhou, Jeffrey Venezuela, Mingxing Zhang, Jianqiu Wang, and Andrej Atrens. "A review of the influence of hydrogen on the mechanical properties of DP, TRIP, and TWIP advanced high-strength steels for auto construction." Corrosion Reviews 34, no. 3 (June 1, 2016): 127–52. http://dx.doi.org/10.1515/corrrev-2015-0083.

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AbstractThe literature is reviewed regarding the influence of hydrogen on dual-phase (DP), transformation-induced plasticity (TRIP), and twinning-induced plasticity (TWIP) steels. Hydrogen influences DP steels by decreasing ductility while strengths are largely unaffected. TRIP steels may be susceptible to hydrogen embrittlement (HE) as indicated by the loss of ductility and some brittle fracture features. The literature on the influence of hydrogen on TWIP steels was inconsistent. Some researchers found no significant influence of hydrogen on TWIP steel properties and fully ductile fractures, whereas others found a significant loss of ductility and strength due to hydrogen and some brittle features. Possible countermeasures for HE are tempering for DP and TRIP steels and aluminum alloying for TWIP steels.

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Journal articles on the topic 'Dual Phase steel - DP'

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