Artykuły w czasopismach: „L12 ordered precipitates”

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Sun, Yuanyang, Yuhong Zhao, Huijun Guo, Xiaolin Tian та Hua Hou. "Early Stages of Precipitation in γ' Phase of a Ni–Al–Ti Model Alloy: Phase-Field and First-Principles Study". Science of Advanced Materials 12, № 5 (2020): 746–54. http://dx.doi.org/10.1166/sam.2020.3716.

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The early stages of precipitation process of the γ' phase of a Ni–Al–Ti alloy are investigated by microscopic phase-field and first-principles calculations. The simulated results indicate that a pre-precipitate with L10 structure appears before the L12 ordered phase, and then this metastable phase gradually transforms to L12 ordered phase; finally, the precipitated phase is composed of γ' ordered phase and γ matrix phase. The occupation probabilities of Al, Ni, and Ti atoms also illustrate the formation of the L10 phase and its situ conversion to L12 ordered phase constituted by a complicated compound Ni3(AlTi). Through the analyses of order parameter and occupation probability, the precipitation mechanism of γ' phase is drawn as a combination of congruent ordering and destabilization decomposition. Meanwhile, we also find that the growth and coarsening of the γ' phase occur via mixed mechanisms of Ostwald ripening and coalescence coarsening of neighboring precipitates. Moreover, the first-principles method is applied to calculate the thermodynamic parameters and validate further the appearance of the metastable phase and the site preference of Ti atom, which offers an explanation for atomic occupancy characteristics in the precipitate.

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Doi, Minoru. "Two-Phase Microstructures Formed by Phase-Separation of Coherent Precipitates in Elastically Constrained Alloy Systems." Materials Science Forum 638-642 (January 2010): 2215–20. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.2215.

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Coherent two-phase microstructures consisting of ordered precipitate and disordered matrix phases sometimes exhibit a phase-separation, which brings the split and/or the decelerated coarsening of precipitates. When the coherent two-phase microstructure of A1+L12 (+’) in Ni-base alloys are aged inside the two-phase region of A1+L12 , the L12 precipitate sometimes exhibit a phase-separation and A1 phase newly appears and grows in each L12 precipitate. Phase-separations of the same type to the above also take place due to ageing of coherent two-phase microstructures of A2+D03 and A2+B2 in Fe-base alloys: D03 and B2 precipitates sometimes exhibit phase-separations and A2 phase newly appears and grows in both precipitates. These types of phase-separation take place under the influence of chemical free energy. In the course of further ageing, the new disordered phases of A1 and A2 change their morphology in various ways depending on the elastic constraint: i.e. the morphology of new A1 or A2 phase is influenced by the elastic energies and the surface energy.

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Zhao, Bing Bing, Xian Ping Dong, Feng Sun, and Lan Ting Zhang. "Impact of L1₂-Ordered Precipitation on the Strength of Alumina-Forming Austenitic Heat-Resistant Steels." Materials Science Forum 941 (December 2018): 692–97. http://dx.doi.org/10.4028/www.scientific.net/msf.941.692.

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Alumina-forming austenitic (AFA) heat-resistance steels firstly developed by Yamamoto et al. at Oak Ridge National Laboratory have been reported as a new promising class of steels with potential for use in high temperature applications in recent years. The creep resistance of AFA steels is improved mainly by precipitation strengthening. Besides modifying the typical existing precipitates, i.e. MC and M23C6 type carbides, B2-NiAl and Fe2Nb-type Laves phase, introduction of coherent L12-ordered precipitate is highly desired. L12-ordered phase gamma prime (γ’) is the most important precipitate for high-temperature strengthening in Ni-based superalloys. In the present work, we demonstrate that addition of 2.8 wt. % Cu to an AFA steel promotes the formation of an L12-ordered phase with the dominating elements Ni, Cu and Al. TEM characterization after slow rate tensile tests indicated there were the different precipitation behaviours at 700°C and 750°C. It was revealed that the occurrence of L12-ordered Ni-Cu-Al phase depends on temperature and Ni content. This opens up new opportunities to promote the formation of L12-ordered phase in Fe-based austenitic heat-resistance steels and benefit high-temperature mechanical properties.

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De Hosson, J. T. M. "Superlattice dislocations in L12 ordered alloys and in alloys containing L12 ordered precipitates." Materials Science and Engineering 81 (August 1986): 515–23. http://dx.doi.org/10.1016/0025-5416(86)90288-0.

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Gayle, Frank W., and John B. VanderSande. "Characterization of Rapidly Solidified Aluminum-Lithium Alloys." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 26–29. http://dx.doi.org/10.1017/s0424820100117224.

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Aluminum-lithium alloys are presently the subject of much research due to the effectiveness of lithium in reducing density, raising elastic modulus and providing for high strength. The strengthening precipitate is the metastable, L12-ordered Al3Li (Cu3Au prototype), or δ'. In binary alloys, δ’ precipitates homogeneously with a spherical shape, coherent with the aluminum matrix. These lithium-containing alloys suffer from poor ductility and fracture toughness, however, which has been attributed to 1) the shear-able nature of the δ’ precipitate, resulting in work softening and slip localization on the relevant slip planes, and 2) precipitate free zone formation along high angle grain boundaries.In a previous paper we proposed that Zr could partially substitute for Li in δ', resulting in a ternary Al3(Li,Zr) phase, which we call δ”. It was anticipated that such a phase would be more resistant to dislocation shear than δ’ from observation of deformation behavior of Al-Zr alloys containing the coherent L12-ordered Al3Zr precipitate.

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Moritani, Tomokazu, Masahiro Ota, Takao Kozakai, and Minoru Doi. "TEM Observations of Two-Phase Microstructure Formed by Phase Separation of Gamma-Prime Precipitates in Ni-Al-Si Alloys." Materials Science Forum 561-565 (October 2007): 2361–64. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.2361.

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The phase-separation behaviour of γ’ precipitates in Ni-7.1Al-6.7Si alloy was investigated by means of transmission electron microscopy (TEM). When the alloy is aged at 1173K, coherent spherical γ’ particles having ordered L12 structure appear in γ matrix having disordered A1 structure. When the two-phase microstructure of γ + γ’ is aged at 973K, spherical γ particles precipitate in the individual γ’ precipitates. In the course of ageing at 973K, the new γ particles grow keeping the spherical shape, their number gradually decreases and finally γ particles aging at 1173K gradually change their shape from sphere to cuboid, but do not practically change their size, i.e. such phase-separation behaviour brings the decelerated growth of γ’ precipitates.

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Wang, Rui, Yilei Fu, Guoliang Xie, Zifan Hao, Shuai Zhang, and Xinhua Liu. "The Microstructure and Mechanical Properties of Cu-20Ni-20Mn Alloy Fabricated by a Compact Preparation Process." Metals 10, no. 11 (2020): 1528. http://dx.doi.org/10.3390/met10111528.

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A novel compact preparation process has been developed to produce a Cu-20Ni-20Mn alloy. This process involves heating-cooling combined mould (HCCM) continuous casting, a solution treatment at 800 °C, rolling at room temperature and a final ageing step at 450 °C. This process eliminates two hot deformation processes, namely, hot forging and hot rolling, greatly improving production efficiency and reducing production costs compared with the traditional preparation process. The alloy fabricated by this process was found to have excellent mechanical properties. Additionally, the formation of precipitated phases during the ageing step is accelerated by this new process. The hardness of the samples reaches 476 HV after ageing for 10 h. Stable, ordered precipitates of Ni3Mn(L12 phase) are observed in the rolled specimen, and the orientation relationship between the copper matrix and ordered Ni3Mn phase (L12 phase) is [200]Cu//[010]Ni3Mn and [011]Cu//[011]Ni3Mn. Precipitation strengthening is the main reason for the increase of strength of the sample during the ageing process. The mechanical properties and ageing precipitation process of the alloy are affected by the rolling process. The precipitation rate of the rolled sample is greatly increased during the ageing process, leading to a larger amount of precipitates.

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Jang, Ok Jun, Cheol-Woong Yang, and Dong Bok Lee. "Transmission Electron Microscopy Characterization of Thermomechanically Treated Al3Ti–(8, 10, 15)% Cr Intermetallics." Microscopy and Microanalysis 19, S5 (2013): 89–94. http://dx.doi.org/10.1017/s1431927613012403.

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AbstractThe ordered L12-type Al3Ti–(8, 10, 15)% Cr intermetallic compounds, namely, Al67Ti25Cr8, Al66Ti24Cr10, and Al59Ti26Cr15, were prepared by induction melting followed by thermomechanical treatment. Their microstructure, compositional variation, and crystal structure were characterized using X-ray diffraction, optical microscopy, and scanning and transmission electron microscopy equipped with energy-dispersive spectroscopy. The Al67Ti25Cr8 alloy consisted of the L12-Al3Ti matrix and precipitates of α2-Ti3Al, D022-Al3Ti, and γ-TiAl. The Al66Ti24Cr10 and Al59Ti26Cr15 alloys consisted of the L12-Al3Ti matrix and grains of α-TiAl and β-Cr.

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Eggeler, Y. M., K. V. Vamsi, and T. M. Pollock. "Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys." Annual Review of Materials Research 51, no. 1 (2021): 209–40. http://dx.doi.org/10.1146/annurev-matsci-102419-011433.

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The mechanical properties of superalloys are strongly governed by the resistance to shearing of ordered precipitates by dislocations. In the operating environments of superalloys, the stresses and temperatures present during thermomechanical loading influence the dislocation shearing dynamics, which involve diffusion and segregation processes that result in a diverse array of planar defects in the ordered L12 γ′ precipitate phase. This review discusses the current understanding of high-temperature deformation mechanisms of γ′ precipitates in two-phase Ni-, Co-, and CoNi-base superalloys. The sensitivity of planar fault energies to chemical composition results in a variety of unique deformation mechanisms, and methods to determine fault energies are therefore reviewed. The degree of chemical segregation in the vicinity of planar defects reveals an apparent phase transformation within the parent γ′ phase. The kinetics of segregation to linear and planar defects play a significant role in high-temperature properties. Understanding and controlling fault energies and the associated dislocation dynamics provide a new pathway for the design of superalloys with exceptional properties.

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Vorontsov, V. A., R. E. Voskoboinikov, and Catherine M. F. Rae. "Prediction of Mechanical Behaviour in Ni-Base Superalloys Using the Phase Field Model of Dislocations." Advanced Materials Research 278 (July 2011): 150–55. http://dx.doi.org/10.4028/www.scientific.net/amr.278.150.

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The “Phase-Field Model of Dislocations” (PFMD) was used to simulate shearing of gamma-prime precipitate arrays in single crystal turbine blade superalloys. The focus of the work has been on the cutting of the L12 ordered precipitates by a<112>{111} dislocation ribbons during Primary Creep. The Phase Field Model presented incorporates specially developed Generalised Stacking Fault Energy (–surface) data obtained from atomistic simulations. The topography of this surface determines the shearing mechanisms observed in the model. The merit of the new –surface, is that it accounts for the formation of extrinsic stacking faults, making the model more relevant to creep deformation of superalloys at elevated temperatures.

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Rakoczy, Łukasz, Bogdan Rutkowski, Małgorzata Grudzień-Rakoczy, Rafał Cygan, Wiktoria Ratuszek та Anna Zielińska-Lipiec. "Analysis of γ′ Precipitates, Carbides and Nano-Borides in Heat-Treated Ni-Based Superalloy Using SEM, STEM-EDX, and HRSTEM". Materials 13, № 19 (2020): 4452. http://dx.doi.org/10.3390/ma13194452.

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The microstructure of a René 108 Ni-based superalloy was systematically investigated by X-ray diffraction, light microscopy, energy-dispersive X-ray spectroscopy, and electron microscopy techniques. The material was investment cast in a vacuum and then solution treated (1200 °C-2h) and aged (900 °C-8h). The γ matrix is mainly strengthened by the ordered L12 γ′ phase, with the mean γ/γ′ misfit, δ, +0.6%. The typical dendritic microstructure with considerable microsegregation of the alloying elements is revealed. Dendritic regions consist of secondary and tertiary γ′ precipitates. At the interface of the matrix with secondary γ′ precipitates, nano M5B3 borides are present. In the interdendritic spaces additionally primary γ′ precipitates, MC and nano M23C6 carbides were detected. The γ′ precipitates are enriched in Al, Ta, Ti, and Hf, while channels of the matrix in Cr and Co. The highest summary concentration of γ′-formers occurs in coarse γ′ surrounding MC carbides. Borides M5B3 contain mostly W, Cr and Mo. All of MC carbides are enriched strongly in Hf and Ta, with the concentration relationship between these and other strong carbide formers depending on the precipitate’s morphology. The nano M23C6 carbides enriched in Cr have been formed as a consequence of phase transformation MC + γ → M23C6 + γ′ during the ageing treatment.

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Wu, Xiao Lan, Zuo Ren Nie, Sheng Ping Wen, Kun Yuan Gao, and Hui Huang. "New Progress on Er-Containing Micro-Alloying Aluminum Alloys." Materials Science Forum 877 (November 2016): 211–17. http://dx.doi.org/10.4028/www.scientific.net/msf.877.211.

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Erbium is an effective micro-alloying element in aluminum alloys and has been investigated intensively. Similar with the addition of Sc in aluminum alloys, nanosized L12-ordered Al3Er precipitates were formed coherently with the matrix in Er-containing micro-alloying aluminum alloys. Further, in the case of the addition of both Er and Zr, core-shell-structured Al3(ZrxEr1−x) precipitates, instead of Al3Er, were observed in a fine dispersion. Those thermally-stable precipitates can refine the grain size, minimize the segregation, homogenize the microstructure, enhance the strength, hinder the recrystallization, and thus improve the comprehensive performance of the aluminum alloys. This paper presents the effect of Er on the microstructure, mechanical properties and thermal stability of aluminum alloys. The research of some typical commercial aluminum alloys containing Er, is also reviewed here.

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Lin, L. S., G. W. Levan, S. M. Russell, and C. C. Law. "Effect of hafnium addition on a Ni-Al-Co Alloy." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (1990): 940–41. http://dx.doi.org/10.1017/s0424820100177830.

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Recent efforts at P&W have shown that the addition of cobalt to binary NiAl results in an appreciable increase in room temperature ductility. One version of this ternary alloy, designated VIM A, has a composition of Ni-30 at.% Al-35 at.% Co. The addition of 0.5 at.% Hf to this alloy (designated VIM AH) results in an improvement in yield strength at 760°C. Room temperature properties were not found to be significantly affected by the Hf addition. This discussion will focus on the microstructures of alloys VIM A and VIM AH and their relationship to the mechanical properties observed in compression at room temperature and 760°C.The addition of hafnium reduced the grain size of VIM AH alloy. After room temperature compression, both alloys show an ordered bcc (B2) matrix and precipitates which are distributed primarily along grain boundaries. These precipitates were identified by microdiffraction to be ordered fcc (L12) gamma prime for VIM A and hexagonal (A3) for VIM AH.

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Ohno, Katsumi, Tadaharu Yokokawa, Toshihiro Yamagata, Hiroshi Harada, Michio Yamazaki та Kazumasa Ohsumi. "Determination of the Coherency Strain of γ and γ′ Phases in Nickel-Base Superalloys at High Temperatures". Advances in X-ray Analysis 36 (1992): 515–26. http://dx.doi.org/10.1154/s0376030800019145.

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AbstractA method for using syncrotoron-radiation parallel-beam X-ray diffractometry for precise lattice parameters and strains of γ-γ′ type Nickel base superalloys at elevated temperature is described. The superalloys have γ′ precipitates which are an ordered L12 structure based on Ni3Al, in y-matrices having a disordered FCC structure. Lattice misfit between γ and γ′ phases was very small and peaks reflected from γ and γ′ phases made unresolved clusters of peaks.Profile fitting with a pseudo-Voigt function is used to resolve overlapping peaks. Instrumental broadening of the peak profile was removed using a deconvolution method. The standard errors of the calculated peak angle were less than 0.002°. The elastic strain of the γ′ precipitates in the alloys were smaller than those of γ-matrices.

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Lin, L. S., G. W. Levan, S. M. Russell, and C. C. Law. "Effect of titanium addition on a Ni-Al-Co alloy." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (1990): 938–39. http://dx.doi.org/10.1017/s0424820100177829.

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AEM examinations of a NiAlCo alloy of composition Ni-29 at.% Al-21 at.% Co after room temperature compression show that the microstructure consists of a twinned tetragonal matrix (L10, marked A in Figure 1a) and ordered fcc gamma prime precipitates (L12, marked B in Figure 1a) along grain boundaries. The compressive yield strengths of this alloy at room temperature and 760°C are 754 MPa and 163 MPa respectively. It also has superior room temperature ductility as compared to binary NiAl. An addition of 5 at.% Ti at the expense of Ni was made to this alloy in order to increase the yield strengths. The quarternary alloy shows compressive yield strengths of 976 MPa and 403 MPa at room temperature and 760°C, respectively, indicating that the Ti addition is having the desired effect.Comparison of the microstructures of the two alloys after room temperature compression (Figures la and lb) shows that the Ti containing alloy has a smaller grain size. X-ray diffraction data indicate that the gamma prime volume fraction increases from 10% to 20% as the result of the Ti addition. Titanium was also found to stabilize the B2 matrix (marked A in Figure lb) as no tetragonal L10 phase was found. All precipitates along grain boundaries were identified by micro-diffraction to be gamma prime.

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Lee, Kap Ho, Yeung Jo Lee, and Kenji Hiraga. "Precipitation behavior in the early stage of aging in an Al–Li°Cu–Mg–Zr–Ag (Weldalite 049) alloy." Journal of Materials Research 14, no. 2 (1999): 384–89. http://dx.doi.org/10.1557/jmr.1999.0056.

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The precipitation behavior of various phases during the aging process of an Ag–Li°Cu–Mg–Zr–Ag (Weldalite 049) alloy was investigated by high-resolution electron microscopy and in situ hot-stage microscopy. Two kinds of domains with L12-type ordered structures, which are considered to be δ′ and β′ phases, are observed with different domain sizes in the alloy quenched from 530 °C. In the early stage of aging at 190 °C, the δ′ phase is precipitated as surrounding the β' phase, and the δ′ domains appear with in-phase and antiphase relationships to the β′ lattices. In situ observations at 190 °C clearly show that the T1 phase precipitates predominantly on dislocations at subgrain boundaries and then is homogeneously formed in the matrix with increasing aging time. The nucleation of the S′ phase is associated with clustering of Cu and Mg in the matrix, and the S0 domains are grown with {210} habit planes.

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Inuzuka, Yusuke, Shogo Ito, Takao Kozakai, and Minoru Doi. "TEM Observations of Precipitation of Coherent L1₂ and D0₂₂ Ordered Phases in Ni-V-Ge Alloys." Materials Science Forum 561-565 (October 2007): 2365–68. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.2365.

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Phase separations of A1 (γ) supersaturated solid solution into γ, cubic-L12 (γ') and tetragonal-D022 (γ") phases were investigated in Ni-V-Ge alloys by means of transmission electron microscopy (TEM). When Ni-15.8at%V-9.0at%Ge alloy is aged at 1073 K, at the early stage of ageing γ" phases are observed in the γ matrix as triangle- or diamond-shaped precipitates. With further ageing, colonies of lamellar structure consisting of two variants of γ" phase are dispersedly formed in the γ matrix and then γ" plates grow along the <110> direction. When Ni-14.5at%V-8.8.at%Ge alloy is isothermally annealed at 1023 K, first spherical γ' particles precipitate homogeneously in the γ matrix, followed by the formation of lamellar structure of γ" phases. In the course of further ageing, the lamellar structure develops, and only γ' particles around the lamellar structure grow and others gradually fade out.

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Xia, ChangMing, LePing Bu, and Qi Zhou. "Annealing hardening behaviour of cold rolled Al_0.5CoNiCu high-entropy alloy." Journal of Physics: Conference Series 2338, no. 1 (2022): 012050. http://dx.doi.org/10.1088/1742-6596/2338/1/012050.

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Abstract The usually, softening occurs when metals are annealed, while for some special metals or alloys, the abnormal phenomenon of annealing hardening will occur. By means of X-ray diffraction (XRD), metallographic (OM) observation, transmission electron microscopy (TEM) and hardness test, the microstructure and hardness of 79% cold rolled Al0.5CrFeCoNiCu high entropy alloy was studied after isothermal annealing for 1 hour at different temperatures, which revealed the cause of annealing induced hardening of the alloy. The results show that the homogenized high-entropy alloy is a face centered cubic (FCC) biphasic structure with close lattice constant. After annealing at 300-750°C, the microhardness of the alloy is higher than that of the cold rolled alloy (399hv); With the increase of annealing temperature, the hardness increased first and then decreased. After annealing at 500 °C for 1 hour, the hardness reached the peak (489hv). XRD phase analysis shows that the alloy will precipitate body centered cubic (BCC) phase when annealed at 500-950°C and precipitate σ phase when annealed at 700-850 °C; In addition, when annealed at 650°C and above, the dislocation recovery speed in FCC phase is accelerated and recrystallization will occur, resulting in rapid softening of the alloy. TEM observation showed that there were L12 nano-precipitates with ordered structure in the FCC phase of the matrix. Therefore, the reason for the hardness peak of the alloy annealed at 500°C is the joint action of dislocation strengthening and precipitation strengthening (L12 and BCC phases).

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Miyasato, Shelly. "Characterization of the microstructures produced by different solutionizing quench rates in aluminum-lithium alloys." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (1990): 966–67. http://dx.doi.org/10.1017/s0424820100177969.

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The microstructure in lightweight aluminum-lithium alloys produced by two different quench rates after solution heat treatment were investigated using conventional transmission electron microscopy (TEM) and high resolution electron microscopy (HREM). The formation mechanism, size and distribution of the phase δ’ (Al3Li) were compared, since the precipitate affects many of the mechanical properties in the age- hardening Al-Li system. The metastable δ’ phase has the L12 ordered structure based on the fcc lattice with a lattice parameter difference of -0.08% with the aluminum matrix. The equilibrium phase δ (AlLi) nucleates independently with the B32 structure. TEM yields direct evidence of δ’ formation, size and distribution which is unattainable by other methods due to the size of the precipitates and the presence of isostructural β’ (Al3Zr) dispersoids. Small blocks of Al-2.4Li-0.lZr and Al-2.6Li-lCu-0.5Mg-0.5Zr (wt.%) were solutionized at 550°C for 2 hrs, then either quenched in 0°C water or in still, ambient air. Electropolished foils were viewed in a Philips 301 (l00kV) or JEM 200CX (200 kV).

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Jockweg, J., та E. Nembach. "Anisotropy of the critical resolved shear stress of a superalloy containing 6 vol.% L12-ordered γ′-precipitates". Acta Metallurgica et Materialia 43, № 9 (1995): 3295–300. http://dx.doi.org/10.1016/0956-7151(95)00046-x.

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Gwalani, B., V. Soni, D. Choudhuri, et al. "Stability of ordered L12 and B2 precipitates in face centered cubic based high entropy alloys - Al0.3CoFeCrNi and Al0.3CuFeCrNi2." Scripta Materialia 123 (October 2016): 130–34. http://dx.doi.org/10.1016/j.scriptamat.2016.06.019.

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Tin, S., L. Zhang, A. P. Ofori, and Michael K. Miller. "Atomic Partitioning of Platinum and Ruthenium in Advanced Single Crystal Ni-Based Superalloys." Materials Science Forum 546-549 (May 2007): 1187–94. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1187.

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The elemental partitioning characteristics of advanced single crystal Ni-base superalloys containing additions of both Pt and Ru have been investigated using atom probe tomography. Detailed microanalysis revealed Ru additions partitioned preferentially to the disordered matrix, whereas Pt additions tended to partition to the ordered intermetallic γ′ precipitates. The partitioning characteristics of three nominally similar alloys with systematic variations in the levels of Cr, Ru and Pt were investigated. For this particular set of experimental alloys, minor changes in the partitioning characteristics of the constituent elements could be attributed to additions of Cr and Ru. The preferential site occupancy of Pt within the L12 lattice was also statistically quantified with ALCHEMI (atomic site location by channelling enhanced microanalysis). In contrast to the atomic partitioning characteristics of Ru, Pt exhibited a tendency to occupy the Ni sublattice sites in the γ′ structure.

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Yang, R., J. A. Leake, and R. W. Cahn. "A microstructural study of a Ni2AlTi–Ni(Al, Ti)–Ni3(Al, Ti) three-phase alloy." Journal of Materials Research 6, no. 2 (1991): 343–54. http://dx.doi.org/10.1557/jmr.1991.0343.

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Early studies showed that the two-phase ordered alloy of semi-coherent β–Ni2AlTi (L21) and β–Ni(Al, Ti) (B2) exhibits excellent elevated-temperature creep strength, and the precipitation of the “rod-like” γ'–Ni3(Al, Ti) (L12) from either the β or the β' phase improves the room-temperature ductility of the phases concerned. In the present investigation an attempt is being made to combine the above microstructural features in β'–β–γ' three-phase alloys and for this purpose the composition Ni63Al22Ti15, near the β'–γ' edge of the three-phase region in the recently estimated Ni–Al–Ti isotherm at 900 °C, has been selected for detailed study. The expected precipitation of both the β and the γ' phases occurs in the dendritically solidified β' phase after a 1100 °C/3 h homogenization and a 900 °C/115 h anneal, although the original interdendritic γ' phase remains. The morphology of the two types of precipitates and their orientation relationships with the β' parent phase have been examined using transmission electron microscopy and diffraction, and the experimentally obtained data compared with those predicted by Khachaturyan's elastic strain energy theory. The β precipitates are nearly cuboidal in shape and are bounded by interface dislocations of aβ〈100〉 edge type. For the β precipitates, both morphology and orientation relation agree with those predicted by the theory. The γ' precipitates were found to obey the Nishiyama–Wassermann orientation relationship with the parent phase. These precipitates are about 0.5 μm thick and elongated along their 〈211〉 directions, and in all cases consist of two twin-related variants, giving a sword-like morphology. The {11} twin planes, parallel to the {10} of the parent phase, have been identified as the habits of the precipitation. The theory, however, predicts a habit of {0.732, 0, 0.681}γ' type and a Baker–Nutting orientation relationship. This discrepancy has been attributed to the inapplicability of some assumptions made in the theory: equal elastic moduli between parent and product phases and a tetragonal transformation strain based on Bain's model of the bcc → fcc transformation. The presence of diffuse streaks in the diffraction patterns of the parent phase, which can be correlated with the 〈110〉〈10〉 shear waves, suggests high elastic anisotropy and lends credit to Zener's model. Crystallographic consideration shows that this model is feasible for the L21 → L12 transformation and explains the observed morphological features of the γ' precipitates. Some earlier studies are also discussed.

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Yang, Y., P. Mukherjee, and P. Sanders. "Precipitation Hardening via Chemically Ordered L12 Precipitates in Al-Sc-Zr Alloys— New Insights Using Combined STEM and EDS Study." Microscopy and Microanalysis 25, S2 (2019): 2188–89. http://dx.doi.org/10.1017/s143192761901167x.

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Zarkevich, Nikolai A., Timothy M. Smith, Eli N. Baum, and John W. Lawson. "Compositional Glass: A State with Inherent Chemical Disorder, Exemplified by Ti-rich Ni3(Al,Ti)1 D024 Phase." Crystals 12, no. 8 (2022): 1049. http://dx.doi.org/10.3390/cryst12081049.

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A compositional glass is a state with an unavoidable disorder in chemical compositions on each site, characterized by frustration and freezing of the compositional degrees of freedom at low temperature. From this state a full atomic long-range order is unachievable by a reasonable thermodynamic treatment. There is a similarity between a spin glass (a magnetic state with disorder in spin orientations) and a compositional glass (with disorder in site occupations by chemical elements): both have frustrated ground states and a frozen disorder at low temperatures T < Tf (here Tf is called the freezing temperature). While it is possible to perform a ground-state search in a compositional glass, the resulting set of the fully ordered structures does not adequately represent the real solid with an inherent atomic disorder. Compositional glasses constitute a class of materials, which is insufficiently understood, but is of high industrial importance. Some of the phases in the precipitated alloys (including steels, high-entropy alloys, and superalloys) might be compositional glasses, and their better understanding would facilitate materials design. Due to their strength at high operating temperatures, superalloys are used in combustion engines and particularly in jet turbine engines. Precipitation strengthening of nickel superalloys is an area of active research. Local phase transformations inside Ni3Al-based precipitates are of particular interest due to their impact on creep strength. In the Ni3(Al1−xTix)1 ternary system, the competing phases are Ni3Al-type L12 (γʹ) and Ni3Ti-type D024 (η), while D019 (χ) is higher in energy. These three phases differ by the stacking of atomic layers: locally, the last two look like the internal and external stacking faults in L12. We compute enthalpies of disordered and ordered Ni3(Al1−xTix)1 ternary structures, examine phase stability, investigate the ground states and competing structures, and predict that the Ti-rich Ni3(Al1−xTix)1 D024 phase is a compositional glass with the atomic disorder on the Al/Ti sublattice. To resolve apparent contradictions among the previous experiments and to confirm our prediction, we perform X-ray diffraction and scanning electron microscopy analysis of the cast Ni3(Ti0.917Al0.083)1 sample. Our measurements appear to confirm the ab initio computed results. Our results elucidate properties of compositional glasses and provide a better understanding of precipitation strengthening mechanisms in Ni superalloys.

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26

de Sá, Maria H., Iikka Isomäki, Jorge A. Ferreira, Marko Hämäläinen, and Maria H. Braga. "Experimental and First Principles Study of the Ni-Ti-W System." Materials Science Forum 730-732 (November 2012): 775–80. http://dx.doi.org/10.4028/www.scientific.net/msf.730-732.775.

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Nickel based superalloys are structural materials with a chemical composition and structure which has been developed to enable good high temperature performances leading to a wider range of applications. Their unique properties are due to their microstructure characterized by the coexistence of L12-ordered intermetallic precipitates like Ni3Al or Ni3Ti - g’ phase - in a face-centered cubic nickel based solid solution matrix, (Ni) - g phase. Solid solution strengthening at high temperatures can also be provided by the addition of refractory alloying elements, like tungsten, W. Therefore, the mechanical properties behaviour of the alloys is very strongly related to their composition and microstructures. The purpose of this work is to study the effect of composition and microstructures in a series of Ni-rich prototype alloys, Ni100-2x–Tix–Wx (in which x is in at.%), in order to understand and ultimately optimize the performance of these materials. The adopted strategy was to combine experimental studies using Neutron Diffraction, Electron Probe Micro Analysis – EPMA, Differential Scanning Calorimeter – DSC and micro-hardness measurements, with first principles calculations for structure optimization and Gibbs energies at different temperatures, for each phase, leading to thermodynamic assessment.

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27

Liu, W., T. Pretorius, H. Rösner, D. Rönnpagel та E. Nembach. "TEM observation and computer simulation of the interaction of superlattice dislocations with disordered γ-precipitates in L12-ordered γ′-(Ni,Co)3(Al,Ti) intermetallics". Materials Science and Engineering: A 234-236 (серпень 1997): 687–91. http://dx.doi.org/10.1016/s0921-5093(97)00374-2.

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Kozakai, Takao, Daisuke Sakurai, and Minoru Doi. "Substitution Effect of the Third Element X on the Morphology of A1/L1₂/D0₂₂ Three-Phase Microstructure in Ni-V-X (X=Si, Al) Alloy." Solid State Phenomena 172-174 (June 2011): 236–41. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.236.

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Morphology of phase-separated microstructure consisting of cubic disordered A1 and ordered L12 phases and tetragonal ordered D022 phase in Ni-V-X (X=Al, Si) alloys has been investigated by transmission electron microscopy. Ternary Ni-V-Al alloy showed the lamellar structure of D022 phase with spherical L12 particles, while Ni-V-Si ternary alloy indicated the anisotropic microstructure consisting of plate- or diamond-shaped D022 and plate-shaped L12 phases. When a part of element Al is substituted by Si, the morphology of three-phase microstructure (A1/L12/D022) varied depending on the amount of element substitution. When Ni-16.1V-4.0Al-2.8Si (at.%) alloy was aged at 1173K for long time, D022 plate-like particle aligned along <110> direction and L12 particles formed between them in the shape of sphere. In the case of Ni-16.6V-2.8Al-4.0Si (at%) alloy more substituted for Al by Si, cuboidal L12 phases were first formed aligning along <100> direction and then plate-shaped D022 phases precipitated along the <100> direction in the channel of cuboidal L12 particles. Such morphological changes with the substitution of the third elements X by Al or Si were able to be explained based on lattice mismatch.

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29

Himuro, Yoshiyuki, Katsumi Koyama, and Yoichiro Bekki. "Precipitation Behaviour of Zirconium Compounds in Zr-Bearing Al-Mg-Si Alloy." Materials Science Forum 519-521 (July 2006): 501–6. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.501.

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In commercial aluminum alloys, Zr is recognized as an important additional element improving their properties such as strength, corrosion resistivily, and so on. It forms very fine particles of the metastable Al3Zr phase with L12 ordered configuration, in the case of alloys without Si. On the other hand, the DO22-type (Al, Si)3Zr phase besides the L12-type Al3Zr phase is precipitated in alloys including large amounts of Si, such as 6000 series. In this study the main stress falls on precipitation behavior of these Zr compounds in a Zr bearing Al-Mg-Si alloy. The Al-0.67Mg-0.97Si-0.37Zr alloy was cast into a metal mold and hot-rolled to a 5 mm thick plate. A lot of fine L12-type Al3Zr particles were coherently precipitated in the matrix by aging the plate at 673K. The aged plate was cold-rolled to a 1 mm thick sheet and annealed at 553-813K, and then microstructure was investigated by using a transmission electron microscope. It was realized that fine coherent L12-type Al3Zr particles are transformed to incoherent and coarse DO22-type (Al, Si)3Zr particles through recrystallization. The DO22-type (Al, Si)3Zr particles reduced recrystallized grain size owing to their pinning effect.

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30

Yao, Q., H. Xing, and J. Sun. "Structural stability and elastic property of the L12 ordered Co3(Al,W) precipitate." Applied Physics Letters 89, no. 16 (2006): 161906. http://dx.doi.org/10.1063/1.2362574.

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Tian, W. H., T. Sano, and M. Nemoto. "Structure of perovskite carbide and nitride precipitates in L10-ordered TiAl." Philosophical Magazine A 68, no. 5 (1993): 965–76. http://dx.doi.org/10.1080/01418619308219379.

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32

Kaneno, Y., T. Nakamura, H. Inoue, and T. Takasugi. "Effect of precipitated Co solid solution on moisture-induced embrittlement of L12-type Co3Ti ordered alloys." Acta Materialia 51, no. 7 (2003): 2113–23. http://dx.doi.org/10.1016/s1359-6454(03)00013-2.

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33

Makineni, Surendra Kumar, Mahander Pratap Singh, and Kamanio Chattopadhyay. "Low-Density, High-Temperature Co Base Superalloys." Annual Review of Materials Research 51, no. 1 (2021): 187–208. http://dx.doi.org/10.1146/annurev-matsci-080619-014459.

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Co base superalloys strengthened by coherent L12 ordered γ′ precipitate in a disordered face-centered cubic γ matrix represent a new opportunity for high-temperature alloy development. The emergence of alloys with low density and high specific yield strength at elevated temperatures has further energized the research and development efforts in the last 5 years. Initially stabilized by the addition of small amounts of Nb and Ta, these new generations of alloys with multiple alloying additions to form basic quaternary and ternary alloys have steadily expanded the property envelopes to raise hope for a modern class of superalloys with higher-temperature capabilities. This article reviews the work of a vibrant set of researchers across the globe whose findings are constantly unlocking the potential of these alloys. These developments have achieved high-temperature strength (at 870°C) >0.6 GPa, γ′ solvus temperature exceeding 1,100°C, and densities between 7.8 and 8.6 g/cm3.

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34

Donlon, W. T., W. E. Dowling, C. E. Cambell, and J. E. Allison. "The effect of thermal exposure on precipitation of Ti3Al(C,N) in Ti-48Al-IV-0.2C." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 1 (1992): 22–23. http://dx.doi.org/10.1017/s0424820100120515.

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Titanium aluminides are attractive candidates for high temperature structural applications because of their high strength to weight ratio at elevated temperatures. The microstructure of these alloys consists of γ-TiAl (distorted L10 structure) , plus α2-Ti3Al (ordered DO19 structure). Varying the heat treatment temperature and cooling rate of these alloys alters the volume fraction and distribution of the γ and α2 phases. This has significant effects on the room temperature ductility. In addition, precipitation of carbides has been observed during high temperature exposure. The effect of these precipitates on the mechanical properties has yet to be determined.Figure 1 shows the general microstructure that was used for this investigation. TEM foils were prepared by electropolishing using 5% perchloric, 35% 1-butanol, 60% methanol at -40°C. No precipitates were found following heat treatment in the γ+α phase field. Samples approximately 20 mm square were thermally exposed to temperatures between 625° and 1000°C for times between 1 and 2000 hours.

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35

Kim, Yong Hwan, Mitsuo Niinomi, Junko Hieda, Masaaki Nakai та Hisao Fukui. "Microstructural Change of β′ Phase and Hardness Change in As-Solutionized Dental Ag-20Pd-12Au-14.5Cu Alloy". Key Engineering Materials 508 (березень 2012): 166–71. http://dx.doi.org/10.4028/www.scientific.net/kem.508.166.

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Change in the Microstructure of the L10-Type Ordered β' Phase Precipitated in Ag-20Pd-12Au-14.5Cu Alloy (mass%) Subjected to Solution Treatment with Varying Solution Treatment Time Was Investigated. The Size of the β' Phase Is Found to Decrease with Increasing Solution Treatment Time and the Vickers Hardness of the Alloy after Solution Treatment Decreases. Experimental Observations Show that the Microstructural Change of the β' Phase Strongly Contributes to the Change in Vickers Hardness. In Addition, the Formation and Growth of the β' Phase Are Concluded to Be Affected by the Distribution of Elements through Solution Treatment.

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36

Maziarz, Wojciech, Jan Dutkiewicz, Rafał Wróblewski та Marcin Leonowicz. "Microstructure and Magnetic Properties of Two Phase β+γ Ferromagnetic Co-Ni-Al Alloys". Solid State Phenomena 154 (квітень 2009): 145–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.154.145.

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The microstructure, texture and magnetic properties of two ferromagnetic alloys of composition Co35Ni37Al28 and Co37Ni35Al28 (in at. %) were investigated with optical microscopy (OM), analytical transmission electron microscopy (TEM), scanning electron microscopy (SEM) techniques as well as a vibrating sample magnetometer (VSM). The alloys were plastically deformed and heat treated in order to promote the martensitic transformation. Differential scanning calorimetry (DSC) revealed a drop of Ms temperature due to the increase of Co content in the alloys. The elongated twinned grains of size about 200 m and small precipitates of  phase were identified with the OM techniques. The TEM observations showed the twinned L10 non modulated martensite within the elongated grains and a small amount of ordered ’ phase after the heat treatment. The chemical composition of different martensite grains was established using point analyses of a HAADF-EDS technique. The magnetic phase transition temperatures were determined on the deformed samples using VSM method.

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37

Cantando, Elizabeth D., Gerard M. Ludtka, Gail Mackiewicz-Ludtka, and William A. Soffa. "Electron Microscopy Study of Hypostoichiometric Fe-Pd Nanocomposites Resulting from Combined Reactions Thermomechanical Processing." Solid State Phenomena 172-174 (June 2011): 356–61. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.356.

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Hypostoichiometric Fe-Pd binary alloys (35-45 at% Pd) were severely deformed (>90%) and subsequently aged to induce concomitant recrystallization, precipitation, and ordering. This thermomechanical processing strategy was articulated by Hornbogen [1] over thirty years ago. The resulting exchange-coupled ferromagnets contain ferrite precipitates and a complex metastable two-phase lamellar transformation product comprised of ordered L10 and a metastable FCC phase. The later duplex microconstituent is suggested to form in conjunction with a so-called pseudospinodal reaction [2] involving emerging cubic and tetragonal phases, whereby phase separation and ordering result from continuous changes in composition and a reduction in symmetry, cubic to tetragonal. The deformation texture of the parent austenite is substantially retained in the transformation product, resulting in anisotropy of the magnetic properties as determined by magnetometry (VSM). This paper presents electron microscopy results elucidating the crystallography and morphology of the phase mixtures including HREM. Magnetic field annealing is also included as a branch of our thermomechanical processing strategy, and we discuss the influence of the external fields on recrystallization, precipitation, and ordering.

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38

Tian, Wen Huai, Takeshi Sano, and Minoru Nemoto. "Hardening Mechanisms in a γ′-L1₂ Ordered Phase Containing Disordered γ Precipitates." Journal of the Japan Institute of Metals 53, no. 10 (1989): 1029–34. http://dx.doi.org/10.2320/jinstmet1952.53.10_1029.

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Tian, Wen Huai, Takeshi Sano, and Minoru Nemoto. "Temperature Dependence of the Yield Stress in γ′-L1₂ Ordered Ni₃(Al, Ti) Single Crystals Containing Disordered γ Precipitates." Journal of the Japan Institute of Metals 54, no. 3 (1990): 276–84. http://dx.doi.org/10.2320/jinstmet1952.54.3_276.

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Tian, Wen Huai, Takeshi Sano, and Minoru Nemoto. "Orientation Dependence of the Yield Stress in γ′-L1₂ Ordered Ni₃(Al, Ti) Single Crystals Containing Disordered γ Precipitates." Journal of the Japan Institute of Metals 54, no. 3 (1990): 285–91. http://dx.doi.org/10.2320/jinstmet1952.54.3_285.

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Tian, Wen Huai, Takeshi Sano, and Minoru Nemoto. "Deformation Induced Microstructure of L1₂ Ordered γ′-Ni₃(Al, Ti) Single Crystals Containing Fine Dispersion of Disordered γ Precipitates." Journal of the Japan Institute of Metals 53, no. 10 (1989): 1022–28. http://dx.doi.org/10.2320/jinstmet1952.53.10_1022.

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42

Doi, Minoru, Hiroshi Kumagai, Kanako Nakashima, and Takao Kozakai. "Phase-Separations of Coherent Precipitates of Ordered Phases in Elastically Constrained Alloys." MRS Proceedings 980 (2006). http://dx.doi.org/10.1557/proc-980-0980-ii05-26.

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AbstractPhase-separations of coherent precipitates of ordered phases were investigated by means of transmission electron microscopy (TEM) and the theoretical analysis from a thermodynamic point of view. When the two-phase microstructures of A1+L12 in elastically constrained Ni-Al-Ti and Ni-Si-Fe alloys are isothermally heated inside the two-phase region of A1+L12 , coherent L12 precipitate particles sometimes exhibit a phase-separation and A1 phase newly appears and grows in L12 particles. Phase-separations of the same type as the above are also observed in coherent two-phase microstructures of A2+D03 and A2+B2 in elastically constrained Fe-Si-V and Fe-Al-Ni alloys respectively: coherent D03 or B2 precipitates exhibit a phase-separation and A2 phase newly appears and grows in both precipitates. Such phase-separation is realized under the influence of chemical free energy and elastic energies.

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43

Nemoto, M., W. H. Tian, and K. Hayashi. "Phase Decomposition and Deformation of L12-Ordered Co-Rich Co3Ti." MRS Proceedings 364 (1994). http://dx.doi.org/10.1557/proc-364-849.

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AbstractThe Co3Ti phase hardens appreciably by the fine precipitation of disordered fee Co-rich phase upon aging after quenching from solution annealing temperature. Transmission electron microscope(TEM) observations revealed that the precipitates are platelet in shape, lying nearly parallel to the {100} planes of the L12-ordered matrix, and perfectly coherent with the matrix lattice at the beginning of aging. The high temperature strength increases appreciably with the fine precipitation of disordered Co-rich phase over the whole temperature range investigated. TEM observations of the underaged and deformed alloys revealed that superdislocations are pinned by precipitates indicating an attractive interaction between dislocations and precipitates. At the overaged state, thin twins are introduced in the fee Co-rich precipitates during deformation.

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44

Dasari, Sriswaroop, Abhishek Sharma, Stéphane Gorsse, Advika Chesetti, and Rajarshi Banerjee. "Non-classical nucleation of ordered L12 precipitates in the FCC based Al0.25CoFeNi high entropy alloy." Journal of Applied Physics 134, no. 1 (2023). http://dx.doi.org/10.1063/5.0138924.

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The complex interplay between competing phase stabilities of FCC, L12, BCC, and B2 phases in the Al0.25CoFeNi (7Al-31Co-31Fe-31Ni in at. %) high entropy alloy (HEA) leads to non-classical phase transformation pathways and resultant novel microstructures. Specifically, the competition between the homogenous precipitation of L12 and heterogenous precipitation of BCC/B2 can be studied at a temperature of 500 °C in the Al0.25CoFeNi alloy. Upon isothermally annealing the single FCC phase microstructure of this HEA at 500 °C up to 50 h, the transformation initiates with the formation of a transient ordered L12 phase with minor Ni–Al enrichment, which is far-from equilibrium, as revealed by atom probe tomography, and can be considered non-classical nucleation. The near equilibrium L12 phase eventually replaces the transient L12 during continued annealing at the same temperature. However, the resultant FCC + L12 microstructure is metastable because the true equilibrium for the Al0.25CoFeNi alloy at 500 °C is a mixture of L12 + B2 phases, as revealed by solution thermodynamics modeling. The higher nucleation barrier for the BCC-based ordered B2 phase coupled with the slower kinetics at 500 °C leads to the homogeneous precipitation of L12, while the B2 phase appears to sluggishly grow from grain boundaries acting as heterogeneous nucleation sites.

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45

Miller, M. K. "Characterization of the Early Stages of Phase Separation by Atom probe Tomography." MRS Proceedings 580 (1999). http://dx.doi.org/10.1557/proc-580-35.

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AbstractAn atom probe tomography characterization of the early stages of phase separation in the FeCu-Ni system has been performed. The development of the copper-enriched regions into copper precipitates has been investigated during isothermal ageing at 573 K and 673 K for times up to 10,000 h. The formation and growth of the secondary precipitates in the nickel based superalloy, Alloy 718, have been determined during isothermal ageing at 873 K. These secondary precipitates were found to be a mixture of the L12-ordered γ' phase and the DO22-ordered γ” phase.

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46

Cerri, A., R. Schmelczer, P. Schwander, G. Kostorz, and A. F. Wright. "Combined Use of Small Angle Neutron Scattering (Sans) and (Conventional and High Resolution) Electron Microscopy for the Characterization of Early Stages of Ordering and Phase Separation in Ni-Ti." MRS Proceedings 82 (1986). http://dx.doi.org/10.1557/proc-82-169.

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ABSTRACTThe decomposition of Ni ∼ 11.5 at.% Ti single crystals was studied for an ageing temperature of 540°C. In this alloy, coherent ordered zones of γ′-Ni3Ti (Cu3Au structure) are formed prior to the stable n precipitates. The early stages of zone formation were investigated by in-beam SANS and transmission electron microscopy (TEM). Electron diffraction, high resolution electron microscopy, TEM analysis of dislocation arrangements in samples deformed after ageing and X-ray measurements of the integrated intensity at L12 superstructure positions show that ordered regions already appear in quenched samples, whereas compositional changes, as determined by SANS measurements, occur only upon ageing.

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47

Ju, Yinfei, Yongsheng Li, Shujing Shi, Peng Sang, Huiyu Wang та Hongli Long. "Phase-Field Simulation of γ′-Co3 (Al, W) Evolution Kinetics with Antiphase Boundaries in Co-Based Monocrystal Superalloys". Frontiers in Materials 9 (30 березня 2022). http://dx.doi.org/10.3389/fmats.2022.872148.

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Antiphase boundaries (APBs) of L12 ordered γ′-Co3 (Al, W) precipitates have an essential effect on the high-temperature strength of Co-based monocrystal superalloys. In this work, the antiphase boundaries and their effects on the evolution kinetics of γ′ phase are studied with the phase-field model. The formation of APBs between γ′ phases with different crystallographic variants induces a sharp increase in free energy; the width of APBs measured by the edge-to-edge distances of the γ′ phase is consistent with the experimental results of superalloys. Also, a coupling behavior of Ostwald ripening and APB’s migration in the coarsening of the γ′ phase is revealed. In addition, the volume fraction of the γ′ phase with four antiphase domains is lower than that of the single-domain γ′ phase, and the time exponent of the particles’ number density of the γ′ phase at the steady coarsening stage changes from –0.99 of single domain to –0.8 of APBs. The results show that the high-energy APBs can reduce the coarsening rate of γ′ phases, which are significant in the microstructure and composition designing of the ordered precipitates with APBs in Co-based superalloys.

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48

Sarkar, Suman, Shyam Kanta Sinha, Dhanalakshmi Palaniswamy, Chandan Srivastava, and Kamanio Chattopadhyay. "Evolution of L12 Ordered Precipitates in Cu–Fe–Si Alloy System and Its Influence on Potential Strength–Conductivity Properties." Metallography, Microstructure, and Analysis, February 17, 2023. http://dx.doi.org/10.1007/s13632-023-00938-2.

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Yasuda, Hiroyuki Y., Mitsuhiro Aoki, Kouki Fukushima, and Yukichi Umakoshi. "Pseudoelastic Behavior of Fe3Ga Single Crystals with D03 Structure." MRS Proceedings 980 (2006). http://dx.doi.org/10.1557/proc-980-0980-ii06-08.

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AbstractPseudoelastic behavior of Fe3Ga single crystals regardless of a thermoelastic martensitic transformation was investigated focusing on the dislocation structure and the phase constituent. Large pseudoelasticity of 5 % recoverable strain appeared in Fe3Ga single crystals sufficiently annealed in the D03 single-phase region. In the crystals, uncoupled and paired 1/4[111] superpartial dislocations moved dragging the nearest-neighbor (NN) and next-nearest neighbor (NNN) anti-phase boundaries (APBs) during loading, respectively. During unloading, these APBs pulled back the superpartials resulting in large pseudoelasticity, which is similar to D03-ordered Fe3Al crystals. The dislocation configuration was closely related to the ordered domain structure developed in the D03 phase. Moreover, the precipitation of the thermally stable L12 phase was so slow that the metastable D03 phase developed even if the crystals were annealed in the (a+ L12) and (D03+ L12) phase fields in Fe-Ga equilibrium phase diagram. The metastable D03 phase also demonstrated large pseudoelasticity of which recovery ratio was above 80 %. On the other hand, if the L12 phase precipitated by long time annealing in the (a+ L12) region, the reversible motion of 1/4[111] superpartials was suppressed by the L12 phase resulting in a decrease in recovery ratio. In addition, the crystals aged in the (a+ D03) phase region showed small strain recovery.

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50

Jin, Chengyan, Xinghao Du, Wanpeng Li, et al. "Investigation on an anti-corrosion Cu-rich multiple-principal-element alloy strengthened and toughened by nano-scaled L1₂-type ordered particles." International Journal of Materials Research, May 18, 2022. http://dx.doi.org/10.1515/ijmr-2021-8677.

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Abstract In this study, the microstructure and mechanical properties of a Cu-rich multiple-principal-element alloy with the composition (Cu50Ni20Cr20Mn10)95Al5 (at.%) were investigated. It was found that after 900 °C/1 h annealing process, the as-cast alloy has achieved promising mechanical properties with a yield stress of 510 MPa, an ultimate tensile stress of 820 MPa and tensile elongation of 30 %. These properties are superior to those of traditional nickel–aluminum bronze (NAB) alloys. Moreover, the as-annealed alloy exhibited much better anti-corrosion properties with respect to the NBA alloys. Transmission electron microscopy observations showed that high-number-density nano-scaled L12-type ordered particles have precipitated in the Cu-rich phase after heat treatment and this was regarded as the main mechanism responsible for the enhancement of yield stress.

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