Pub Date : 2026-01-10DOI: 10.1016/j.msea.2025.149685
Xiangyu Wang , Chao He , Yajun Dai , Yongjie Liu , Chong Wang , Qingyuan Wang
This work investigates the mechanisms governing micropore nucleation and fatigue crack propagation in a directionally solidified (DS) Ni-based superalloy (IC10) subjected to very high cycle fatigue (VHCF) at 850 °C. By employing advanced characterization techniques, including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and electron channeling contrast imaging (ECCI), we show that fatigue cracks predominantly initiate from internal casting pores and propagate in an {111} planar-slip-driven mode. Two distinct modes of early crack growth were identified: (1) a tortuous pathway mediated by interconnected circular and short rod-like micro-voids, and (2) discontinuous propagation along the trace direction of a specific slip-plane. Our observations further demonstrate that such crack-growth behavior is strongly influenced by localized microstructural evolution, including cyclic slip-band deformation, the formation of low-angle grain boundaries, and their interactions with the γ/γ′ interface. These coupled processes promote micro-void nucleation and accelerate subsequent crack extension. Overall, the results provide new insights into the VHCF failure of DS Ni-based superalloys and offer guidance for microstructural optimization and life prediction in high-performance DS alloys.
{"title":"VHCF behavior and micro-void formation in a directionally solidified nickel-based superalloy","authors":"Xiangyu Wang , Chao He , Yajun Dai , Yongjie Liu , Chong Wang , Qingyuan Wang","doi":"10.1016/j.msea.2025.149685","DOIUrl":"10.1016/j.msea.2025.149685","url":null,"abstract":"<div><div>This work investigates the mechanisms governing micropore nucleation and fatigue crack propagation in a directionally solidified (DS) Ni-based superalloy (IC10) subjected to very high cycle fatigue (VHCF) at 850 °C. By employing advanced characterization techniques, including scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and electron channeling contrast imaging (ECCI), we show that fatigue cracks predominantly initiate from internal casting pores and propagate in an {111} planar-slip-driven mode. Two distinct modes of early crack growth were identified: (1) a tortuous pathway mediated by interconnected circular and short rod-like micro-voids, and (2) discontinuous propagation along the trace direction of a specific slip-plane. Our observations further demonstrate that such crack-growth behavior is strongly influenced by localized microstructural evolution, including cyclic slip-band deformation, the formation of low-angle grain boundaries, and their interactions with the γ/γ′ interface. These coupled processes promote micro-void nucleation and accelerate subsequent crack extension. Overall, the results provide new insights into the VHCF failure of DS Ni-based superalloys and offer guidance for microstructural optimization and life prediction in high-performance DS alloys.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149685"},"PeriodicalIF":7.0,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-10DOI: 10.1016/j.msea.2026.149763
Wenke Wang , Yu Chen , Zhifei Zhao , Zheyue Ai , Wenhui Guo , Yang Guo , Jianxun Zhang
The micro-region tensile properties of a 12 %Cr/NiCrMoV dissimilar metal welded joint (DMWJ) with a buttering layer were investigated. The yield strength (YS), ultimate tensile strength (UTS), strain hardening exponent, and strain hardening rate were obtained from 54 adjacent tensile specimens. The results showed that the micro-region strength and strain hardening exponent were not uniformly distributed across the DMWJ. The YS values of the 12 %Cr base metal (BM1), buttering layer (BL), weld metal (WM), and 30Cr2Ni4MoV base metal (BM2) were 751 MPa, 613 MPa, 705 MPa, and 793 MPa, respectively. The corresponding UTS values were 860 MPa, 718 MPa, 822 MPa, and 909 MPa. The strain hardening exponents (n2) were 0.079, 0.071, 0.086, and 0.083, respectively. The inferior strength and hardening ability of the BL originated from its blocky ferrite, coarse carbides, low KAM value (0.77°), and relatively coarse grains (3.05 μm). In the heat-affected zones (HAZ1 and HAZ2), strength decreased while the strain hardening exponent increased from the coarse-grain zone (CGZ) toward the fine-grain zone (FGZ), consistent with the gradual refinement of lath martensite. The true stress-strain curves revealed two stages of strain hardening, represented by exponents n1 and n2. The n2 value, which characterizes the middle and late stages of plastic deformation, was more sensitive to microstructural variation. The strength calculated using n2 and microhardness showed good agreement with the measured layered-tensile strength, indicating that the layered tensile method effectively avoids size effects and provides reliable micro-region strength. Micro-region mechanical properties without size-effect could be obtained by layered tensile test, which provides accurate assessment for crack calculation and structural integrity of DMWJs.
{"title":"Micro-region strength and strain hardening behavior of 12 %Cr/NiCrMoV dissimilar metal welded joint of steam turbine rotor","authors":"Wenke Wang , Yu Chen , Zhifei Zhao , Zheyue Ai , Wenhui Guo , Yang Guo , Jianxun Zhang","doi":"10.1016/j.msea.2026.149763","DOIUrl":"10.1016/j.msea.2026.149763","url":null,"abstract":"<div><div>The micro-region tensile properties of a 12 %Cr/NiCrMoV dissimilar metal welded joint (DMWJ) with a buttering layer were investigated. The yield strength (YS), ultimate tensile strength (UTS), strain hardening exponent, and strain hardening rate were obtained from 54 adjacent tensile specimens. The results showed that the micro-region strength and strain hardening exponent were not uniformly distributed across the DMWJ. The YS values of the 12 %Cr base metal (BM1), buttering layer (BL), weld metal (WM), and 30Cr2Ni4MoV base metal (BM2) were 751 MPa, 613 MPa, 705 MPa, and 793 MPa, respectively. The corresponding UTS values were 860 MPa, 718 MPa, 822 MPa, and 909 MPa. The strain hardening exponents (n<sub>2</sub>) were 0.079, 0.071, 0.086, and 0.083, respectively. The inferior strength and hardening ability of the BL originated from its blocky ferrite, coarse carbides, low KAM value (0.77°), and relatively coarse grains (3.05 μm). In the heat-affected zones (HAZ1 and HAZ2), strength decreased while the strain hardening exponent increased from the coarse-grain zone (CGZ) toward the fine-grain zone (FGZ), consistent with the gradual refinement of lath martensite. The true stress-strain curves revealed two stages of strain hardening, represented by exponents n<sub>1</sub> and n<sub>2</sub>. The n<sub>2</sub> value, which characterizes the middle and late stages of plastic deformation, was more sensitive to microstructural variation. The strength calculated using n<sub>2</sub> and microhardness showed good agreement with the measured layered-tensile strength, indicating that the layered tensile method effectively avoids size effects and provides reliable micro-region strength. Micro-region mechanical properties without size-effect could be obtained by layered tensile test, which provides accurate assessment for crack calculation and structural integrity of DMWJs.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149763"},"PeriodicalIF":7.0,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-09DOI: 10.1016/j.msea.2026.149765
Guangjing Liao , Pan Xie , Libo Fu , Hu Li , Guojing Chen , Hailong Cong , Cuilan Wu
Allvac 718Plus (hereafter termed 718Plus) is a polycrystalline nickel-based superalloy developed from the widely used Inconel 718, with the key compositional change being the introduction of cobalt. Despite its commercial use, the site occupancy of Co atoms in δ, η, γ′, and γ″ phases, as well as the influence mechanism of cobalt on the precipitate evolution and mechanical properties of 718Plus, remains insufficiently elucidated. In this study, we systematically investigate the partitioning and role of cobalt in governing grain boundary and intragranular precipitation in polycrystalline 718Plus. The results demonstrate that the majority of the cobalt exhibits a partitioning preference for the γ matrix. In the δ, η, γ′, and γ″ phases, atomic-resolution EDS analyses and first-principles calculations confirm that cobalt preferentially occupies nickel sublattice sites. Increasing cobalt content lowers the solubility of Ni, Nb, and Ti element in the γ matrix and promotes their partitioning into the δ, η, and γ′ precipitates. This redistribution promotes the formation of the η/δ phase during solution treatment. An increase in the η/δ phase fraction not only reduces the volume fraction of the γ″ phase but also that of the γ′ phase when the increase becomes excessive during subsequent aging treatment. Consequently, the diminished γ″ phase fraction enhances plasticity but lowers the tensile and yield strength. Additionally, an excessively high η/δ phase fraction compromises ductility. These findings provide fundamental insight into the cobalt-mediated precipitation mechanisms in nickel-based polycrystalline superalloys and offer valuable guidance for the design of next-generation high-performance alloy compositions.
{"title":"Influence of cobalt content on the precipitates and mechanical properties in nickel-based polycrystalline superalloys","authors":"Guangjing Liao , Pan Xie , Libo Fu , Hu Li , Guojing Chen , Hailong Cong , Cuilan Wu","doi":"10.1016/j.msea.2026.149765","DOIUrl":"10.1016/j.msea.2026.149765","url":null,"abstract":"<div><div>Allvac 718Plus (hereafter termed 718Plus) is a polycrystalline nickel-based superalloy developed from the widely used Inconel 718, with the key compositional change being the introduction of cobalt. Despite its commercial use, the site occupancy of Co atoms in δ, η, γ′, and γ″ phases, as well as the influence mechanism of cobalt on the precipitate evolution and mechanical properties of 718Plus, remains insufficiently elucidated. In this study, we systematically investigate the partitioning and role of cobalt in governing grain boundary and intragranular precipitation in polycrystalline 718Plus. The results demonstrate that the majority of the cobalt exhibits a partitioning preference for the γ matrix. In the δ, η, γ′, and γ″ phases, atomic-resolution EDS analyses and first-principles calculations confirm that cobalt preferentially occupies nickel sublattice sites. Increasing cobalt content lowers the solubility of Ni, Nb, and Ti element in the γ matrix and promotes their partitioning into the δ, η, and γ′ precipitates. This redistribution promotes the formation of the η/δ phase during solution treatment. An increase in the η/δ phase fraction not only reduces the volume fraction of the γ″ phase but also that of the γ′ phase when the increase becomes excessive during subsequent aging treatment. Consequently, the diminished γ″ phase fraction enhances plasticity but lowers the tensile and yield strength. Additionally, an excessively high η/δ phase fraction compromises ductility. These findings provide fundamental insight into the cobalt-mediated precipitation mechanisms in nickel-based polycrystalline superalloys and offer valuable guidance for the design of next-generation high-performance alloy compositions.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149765"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, the mechanical properties and microstructural evolution of a dual-phase HEA, , with hierarchical microstructure, under high strain rate loading (800–3600 ) were systematically investigated. Attributed to the synergistic effect of the characteristic FCC phase and BCC phase, this HEA exhibits an excellent combination of high strength and ductility, maintaining substantial plastic deformation capacity without failure at true strains approaching 0.35, even at a strain rate of 3600 . With increasing strain rate, the dominant plastic deformation mechanism in the FCC phase transitions from dislocation glide to a synergy of dislocation slip and deformation twinning, with twinning significantly enhancing strain hardening and plastic stability. In the BCC phase, dislocation slip remains the principal mechanism, but is severely impeded by the nano-scaled B2 precipitates, thereby contributing to strength enhancement. Both BCC and B2 phases activate double slip systems at elevated strain rates, exhibiting unexpected plastic deformation capability, with B2 precipitates even partially fragmented under extreme loading. The alloy also demonstrates pronounced positive strain rate sensitivity, with the strain rate sensitivity coefficient sharply increasing from 0.019 in the quasi-static regime to 0.214 at high strain rates. Modified Johnson-Cook constitutive models, incorporating strain rate hardening parameter as a function of plastic strain, were developed and show good agreement with experimental results, accurately capturing the strain-rate-dependent plastic response of current dual-phase HEA.
{"title":"Dynamic deformation behavior and mechanisms of a dual-phase high-entropy alloy with hierarchical microstructure","authors":"Shuihan Xiao , Peng Gao , Yupei Guo , Xinke Xiao , Yaxin Zhu , Chunyu Bai , Shuang Liang , Lv Zhao , Minsheng Huang","doi":"10.1016/j.msea.2026.149764","DOIUrl":"10.1016/j.msea.2026.149764","url":null,"abstract":"<div><div>In this study, the mechanical properties and microstructural evolution of a dual-phase HEA, <span><math><mrow><msub><mtext>Al</mtext><mn>0.6</mn></msub><mtext>CoCr</mtext><msub><mtext>Fe</mtext><mn>2</mn></msub><mtext>Ni</mtext></mrow></math></span>, with hierarchical microstructure, under high strain rate loading (800–3600 <span><math><mrow><msup><mi>s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>) were systematically investigated. Attributed to the synergistic effect of the characteristic FCC phase and BCC phase, this HEA exhibits an excellent combination of high strength and ductility, maintaining substantial plastic deformation capacity without failure at true strains approaching 0.35, even at a strain rate of 3600 <span><math><mrow><msup><mi>s</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. With increasing strain rate, the dominant plastic deformation mechanism in the FCC phase transitions from dislocation glide to a synergy of dislocation slip and deformation twinning, with twinning significantly enhancing strain hardening and plastic stability. In the BCC phase, dislocation slip remains the principal mechanism, but is severely impeded by the nano-scaled B2 precipitates, thereby contributing to strength enhancement. Both BCC and B2 phases activate double slip systems at elevated strain rates, exhibiting unexpected plastic deformation capability, with B2 precipitates even partially fragmented under extreme loading. The alloy also demonstrates pronounced positive strain rate sensitivity, with the strain rate sensitivity coefficient sharply increasing from 0.019 in the quasi-static regime to 0.214 at high strain rates. Modified Johnson-Cook constitutive models, incorporating strain rate hardening parameter as a function of plastic strain, were developed and show good agreement with experimental results, accurately capturing the strain-rate-dependent plastic response of current dual-phase HEA.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149764"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-09DOI: 10.1016/j.msea.2026.149756
A.H. Al-Allaq, N. Tabassum, Y.S. Mohammed, A.A. Elmustafa
<div><div>Refractory multi-principal element alloy (MPEA) thin films such as Nb–Mo–Ta–W are promising candidates for high-temperature structural and protective coating applications due to their high melting points and mechanical stability. However, the coupled effects of processing-induced microstructure, oxidation behavior, and the resulting mechanical response in these films remain insufficiently understood. In this work, equiatomic <span><math><mrow><msub><mrow><mi>N</mi><mi>b</mi></mrow><mn>25</mn></msub><msub><mrow><mi>M</mi><mi>o</mi></mrow><mn>25</mn></msub><msub><mrow><mi>T</mi><mi>a</mi></mrow><mn>25</mn></msub><msub><mi>W</mi><mn>25</mn></msub></mrow></math></span> multi-principal element alloy thin films were deposited by DC magnetron sputtering at 0.25 Pa and annealed in air at 250–625 °C to quantify process–structure–property evolution during oxidation, and the influence of deposition conditions and temperature on microstructure, residual stress, oxidation kinetics, and mechanical properties was systematically investigated. X-ray diffraction revealed a bcc (110) fiber-textured solid solution in the as-deposited state, followed by temperature-dependent peak broadening and intensity loss without emergent crystalline oxide reflections; the Scherrer crystallite size decreases from 35.2 ± 1.7 nm at 25 °C to 10.0 ± 0.5 nm at 500 °C, with the 625 °C pattern exhibiting an amorphous-like structure. Cross-sectional imaging showed parabolic oxide growth, from 128 ± 15 nm at 375 °C to 960 ± 50 nm at 500 °C and 3.58 ± 1.00 μm at 625 °C, corresponding to ≈76 % through-thickness expansion; EDS profiles indicated graded oxygen enrichment rather than discrete phase formation. Nanoindentation results suggested a non-monotonic mechanical response: hardness and modulus peaked at 15.6 GPa and 260.5 GPa at 375 °C, then declined to 155.1 GPa at 625 °C as the indentation volume became oxide-dominated. Restricting analysis to the metallic regime (≤375 °C) yielded a Hall–Petch relation <span><math><mrow><mi>H</mi><mspace></mspace><mrow><mo>[</mo><mtext>GPa</mtext><mo>]</mo></mrow><mo>=</mo><mn>5.23</mn><mrow><mo>(</mo><mrow><mo>±</mo><mn>0.45</mn></mrow><mo>)</mo></mrow><mo>+</mo><mn>31.2</mn><mrow><mo>(</mo><mrow><mo>±</mo><mn>3.8</mn></mrow><mo>)</mo></mrow><mspace></mspace><msup><mi>d</mi><mrow><mo>−</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><mspace></mspace><mrow><mo>[</mo><mrow><mi>n</mi><msup><mi>m</mi><mrow><mo>‐</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow><mo>]</mo></mrow></mrow></math></span>, consistent with refinement-driven strengthening. Oxidation kinetics extracted from scale growth gave an apparent activation energy <span><math><mrow><mi>Q</mi><mo>≈</mo><mn>1.2</mn><mo>×</mo><msup><mn>10</mn><mn>2</mn></msup></mrow></math></span> kJ mol<sup>−1</sup> (≈1.2 eV), indicative of diffusion through a mixed amorphous network and short-circuit paths. Peak properties coincided with a small oxide fraction (≈5 vol%) and a strongly compress
{"title":"Annealed Nb25Mo25Ta25W25 thin films: oxidation-induced amorphization, stress-assisted refinement, and property trade-offs","authors":"A.H. Al-Allaq, N. Tabassum, Y.S. Mohammed, A.A. Elmustafa","doi":"10.1016/j.msea.2026.149756","DOIUrl":"10.1016/j.msea.2026.149756","url":null,"abstract":"<div><div>Refractory multi-principal element alloy (MPEA) thin films such as Nb–Mo–Ta–W are promising candidates for high-temperature structural and protective coating applications due to their high melting points and mechanical stability. However, the coupled effects of processing-induced microstructure, oxidation behavior, and the resulting mechanical response in these films remain insufficiently understood. In this work, equiatomic <span><math><mrow><msub><mrow><mi>N</mi><mi>b</mi></mrow><mn>25</mn></msub><msub><mrow><mi>M</mi><mi>o</mi></mrow><mn>25</mn></msub><msub><mrow><mi>T</mi><mi>a</mi></mrow><mn>25</mn></msub><msub><mi>W</mi><mn>25</mn></msub></mrow></math></span> multi-principal element alloy thin films were deposited by DC magnetron sputtering at 0.25 Pa and annealed in air at 250–625 °C to quantify process–structure–property evolution during oxidation, and the influence of deposition conditions and temperature on microstructure, residual stress, oxidation kinetics, and mechanical properties was systematically investigated. X-ray diffraction revealed a bcc (110) fiber-textured solid solution in the as-deposited state, followed by temperature-dependent peak broadening and intensity loss without emergent crystalline oxide reflections; the Scherrer crystallite size decreases from 35.2 ± 1.7 nm at 25 °C to 10.0 ± 0.5 nm at 500 °C, with the 625 °C pattern exhibiting an amorphous-like structure. Cross-sectional imaging showed parabolic oxide growth, from 128 ± 15 nm at 375 °C to 960 ± 50 nm at 500 °C and 3.58 ± 1.00 μm at 625 °C, corresponding to ≈76 % through-thickness expansion; EDS profiles indicated graded oxygen enrichment rather than discrete phase formation. Nanoindentation results suggested a non-monotonic mechanical response: hardness and modulus peaked at 15.6 GPa and 260.5 GPa at 375 °C, then declined to 155.1 GPa at 625 °C as the indentation volume became oxide-dominated. Restricting analysis to the metallic regime (≤375 °C) yielded a Hall–Petch relation <span><math><mrow><mi>H</mi><mspace></mspace><mrow><mo>[</mo><mtext>GPa</mtext><mo>]</mo></mrow><mo>=</mo><mn>5.23</mn><mrow><mo>(</mo><mrow><mo>±</mo><mn>0.45</mn></mrow><mo>)</mo></mrow><mo>+</mo><mn>31.2</mn><mrow><mo>(</mo><mrow><mo>±</mo><mn>3.8</mn></mrow><mo>)</mo></mrow><mspace></mspace><msup><mi>d</mi><mrow><mo>−</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup><mspace></mspace><mrow><mo>[</mo><mrow><mi>n</mi><msup><mi>m</mi><mrow><mo>‐</mo><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow><mo>]</mo></mrow></mrow></math></span>, consistent with refinement-driven strengthening. Oxidation kinetics extracted from scale growth gave an apparent activation energy <span><math><mrow><mi>Q</mi><mo>≈</mo><mn>1.2</mn><mo>×</mo><msup><mn>10</mn><mn>2</mn></msup></mrow></math></span> kJ mol<sup>−1</sup> (≈1.2 eV), indicative of diffusion through a mixed amorphous network and short-circuit paths. Peak properties coincided with a small oxide fraction (≈5 vol%) and a strongly compress","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149756"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-09DOI: 10.1016/j.msea.2026.149766
Dali Li , Hao Liu , Wenqin Wang , Peijian Chen , Jingbin Hao , Haifeng Yang , Xiuli He , Gang Yu
Compared with additive manufacturing, laser cladding involves lower thermal accumulation and a faster cooling rate of the molten pool, the single plastic deformation experienced by each coating track makes it difficult for dynamic recrystallization to be activated solely by the processing energy. In this study, a CoCrFeMnNi high-entropy alloy (HEA) coating with a laminated heterogeneous structure was synchronously fabricated via in-situ thermal rolling assisted laser cladding process. Molecular dynamics simulations revealed that higher temperatures increased strain, promoting the formation of Shockley partial dislocations and stacking faults. Dislocation interactions generated Hirth locks, which hindered dislocation motion and improved plastic deformation resistance. Experimental results showed that the plastic flow induced by thermal field assisted in-situ rolling significantly reduced the porosity and surface roughness of the coating. The application of the thermal field resulted in the formation of a severely plastically deformed band oriented at approximately 45°, within which recrystallization occurred, leading to the formation of fine-grained regions, recrystallization was not observed in the surrounded areas. A laminated heterogeneous structure with alternating coarse and fine grains was formed inside the coating, and the partial recrystallization that occurred during fabrication contributed to the development of this internal heterogeneity. The introduction of the thermal field caused a transition in the recrystallization mechanism within the severely deformed zone, from static recrystallization to dynamic recrystallization. The combined effects of reduced porosity, increased microhardness, and heterogeneous structure strengthening enhanced the mechanical properties of the coating. The microhardness was significantly increased from 214.6HV0.3 to 284.3HV0.3. This study presents a novel approach for designing heterogeneous HEA coatings and clarifies the microstructural evolution mechanisms during fabrication.
{"title":"Construct laminated heterogeneous structures to enhance mechanical properties of CoCrFeMnNi high-entropy alloy coatings by in-situ deformation assisted laser cladding activating dynamic recrystallization","authors":"Dali Li , Hao Liu , Wenqin Wang , Peijian Chen , Jingbin Hao , Haifeng Yang , Xiuli He , Gang Yu","doi":"10.1016/j.msea.2026.149766","DOIUrl":"10.1016/j.msea.2026.149766","url":null,"abstract":"<div><div>Compared with additive manufacturing, laser cladding involves lower thermal accumulation and a faster cooling rate of the molten pool, the single plastic deformation experienced by each coating track makes it difficult for dynamic recrystallization to be activated solely by the processing energy. In this study, a CoCrFeMnNi high-entropy alloy (HEA) coating with a laminated heterogeneous structure was synchronously fabricated via in-situ thermal rolling assisted laser cladding process. Molecular dynamics simulations revealed that higher temperatures increased strain, promoting the formation of Shockley partial dislocations and stacking faults. Dislocation interactions generated Hirth locks, which hindered dislocation motion and improved plastic deformation resistance. Experimental results showed that the plastic flow induced by thermal field assisted in-situ rolling significantly reduced the porosity and surface roughness of the coating. The application of the thermal field resulted in the formation of a severely plastically deformed band oriented at approximately 45°, within which recrystallization occurred, leading to the formation of fine-grained regions, recrystallization was not observed in the surrounded areas. A laminated heterogeneous structure with alternating coarse and fine grains was formed inside the coating, and the partial recrystallization that occurred during fabrication contributed to the development of this internal heterogeneity. The introduction of the thermal field caused a transition in the recrystallization mechanism within the severely deformed zone, from static recrystallization to dynamic recrystallization. The combined effects of reduced porosity, increased microhardness, and heterogeneous structure strengthening enhanced the mechanical properties of the coating. The microhardness was significantly increased from 214.6HV<sub>0.3</sub> to 284.3HV<sub>0.3</sub>. This study presents a novel approach for designing heterogeneous HEA coatings and clarifies the microstructural evolution mechanisms during fabrication.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149766"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study systematically investigates the effects of Zr and Sc microalloying and heat treatment on the microstructure, mechanical properties, and fracture behavior of a squeeze-cast Al-6.5Zn-2.1 Mg-2Cu alloy. The results demonstrate that the co-addition of Sc and Zr promotes the formation of primary Al3(Sc,Zr,Ti) phases, which act as heterogeneous nucleation sites during solidification, refining the as-cast grain size by 58 % and reducing the secondary dendrite arm spacing (SDAS) of α-Al grains by 54 %. A two-stage solution treatment (468 °C × 24 h + 480 °C × 6 h) effectively reduces the volume fraction of residual secondary phases to below 0.3 %. Furthermore, the addition of Sc and Zr accelerates the aging kinetics, shortens the time to peak aging, and enhances peak hardness. In the T6 condition, the alloy with 0.2 wt% Sc and 0.2 wt% Zr achieves a tensile strength of 644 MPa, a yield strength of 577 MPa, and an elongation of 5.7 %. This represents a simultaneous improvement in strength and ductility, with strength levels comparable to those of certain wrought 7000-series aluminum alloys. The enhanced mechanical properties are primarily attributed to grain refinement and Orowan strengthening from aging-induced precipitates.
{"title":"Effects of Sc and Zr microalloying on the microstructure and mechanical properties of a squeeze-cast Al-Zn-Mg-Cu alloy","authors":"Zhimin Wu , Junxu Shi , Shulin Lü , Kewang Xiang , Zhaoxiang Yan , Wenbo Guo , Dijia Zhao , Zhenghua Meng , Shusen Wu","doi":"10.1016/j.msea.2026.149762","DOIUrl":"10.1016/j.msea.2026.149762","url":null,"abstract":"<div><div>This study systematically investigates the effects of Zr and Sc microalloying and heat treatment on the microstructure, mechanical properties, and fracture behavior of a squeeze-cast Al-6.5Zn-2.1 Mg-2Cu alloy. The results demonstrate that the co-addition of Sc and Zr promotes the formation of primary Al<sub>3</sub>(Sc,Zr,Ti) phases, which act as heterogeneous nucleation sites during solidification, refining the as-cast grain size by 58 % and reducing the secondary dendrite arm spacing (SDAS) of α-Al grains by 54 %. A two-stage solution treatment (468 °C × 24 h + 480 °C × 6 h) effectively reduces the volume fraction of residual secondary phases to below 0.3 %. Furthermore, the addition of Sc and Zr accelerates the aging kinetics, shortens the time to peak aging, and enhances peak hardness. In the T6 condition, the alloy with 0.2 wt% Sc and 0.2 wt% Zr achieves a tensile strength of 644 MPa, a yield strength of 577 MPa, and an elongation of 5.7 %. This represents a simultaneous improvement in strength and ductility, with strength levels comparable to those of certain wrought 7000-series aluminum alloys. The enhanced mechanical properties are primarily attributed to grain refinement and Orowan strengthening from aging-induced precipitates.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149762"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-09DOI: 10.1016/j.msea.2026.149768
Chang-tai Jiang , Jin-lai Liu , Jin-jiang Yu , Yi-zhou Zhou , Xiao-feng Sun
This study investigated the effect of overtemperature treatment (OTT) and creep deformation (CD) on the high cycle fatigue (HCF) property on a Ni-based single crystal superalloy. 100 h OTT at 1150 °C, 1180 °C, 1200 °C or 0.5 %, 1 %, 3 % of CD at 1150 °C/100 MPa, 1200 °C/100 MPa were introduced respectively to samples before HCF tests. Compared with the fatigue life of standard heat treatment state sample, the fatigue life of samples after OTT at 1150 °C and 1180 °C, as well as samples after CD, has been improved, while the fatigue life of sample after OTT at 1200 °C has significantly decreased. After OTT at 1150 °C and 1180 °C, a portion of γ′ precipitates connected to form strip-shaped structures, and dislocation networks accumulated at the γ/γ′ interface slowed down the dissolution of γ′ phase. Under the creep stress, γ′ forms raft structure, with a large number of dense dislocation networks accumulating at the interface between matrix and the γ′ phase. The dislocation network hinders the alternating slip of fatigue dislocations in the matrix, reduces the formation of entangled dislocations, resulting in delayed crack initiation and propagation, and prolonged the fatigue life of the alloy. The dense raft structures formed after creep can also effectively hinder crack initiation. For the condition of OTT at 1200 °C, γ′ phase dissolved rapidly, accompanied with the precipitation of a large amount of secondary γ′ phase and the degradation of dislocation networks, which is the main factor leading to the decrease in fatigue life.
研究了过温处理（OTT）和蠕变变形（CD）对ni基单晶高温合金高周疲劳性能的影响。在HCF试验前，分别在1150°C、1180°C、1200°C或1150°C/100 MPa、1200°C/100 MPa下向样品中引入100 h OTT或0.5%、1%、3% CD。与标准热处理状态试样的疲劳寿命相比，经1150℃、1180℃OTT处理后试样的疲劳寿命和经CD处理后试样的疲劳寿命均有提高，而经1200℃OTT处理后试样的疲劳寿命明显下降。在1150°C和1180°C热处理后，部分γ′析出相连接形成条形结构，在γ/γ′界面处积累的位错网络减缓了γ′相的溶解。在蠕变应力作用下，γ′形成筏形结构，在基体与γ′相界面处积聚大量密集的位错网络。位错网络阻碍了疲劳位错在基体中的交替滑移，减少了缠结位错的形成，延迟了裂纹的萌生和扩展，延长了合金的疲劳寿命。蠕变后形成的致密筏状结构也能有效地阻碍裂纹萌生。在1200℃的OTT条件下，γ′相快速溶解，伴随大量次生γ′相的析出和位错网络的退化，这是导致疲劳寿命下降的主要因素。
{"title":"Study on the high cycle fatigue property of a Ni-based single crystal superalloy after overtemperature or creep deformation at elevated temperature","authors":"Chang-tai Jiang , Jin-lai Liu , Jin-jiang Yu , Yi-zhou Zhou , Xiao-feng Sun","doi":"10.1016/j.msea.2026.149768","DOIUrl":"10.1016/j.msea.2026.149768","url":null,"abstract":"<div><div>This study investigated the effect of overtemperature treatment (OTT) and creep deformation (CD) on the high cycle fatigue (HCF) property on a Ni-based single crystal superalloy. 100 h OTT at 1150 °C, 1180 °C, 1200 °C or 0.5 %, 1 %, 3 % of CD at 1150 °C/100 MPa, 1200 °C/100 MPa were introduced respectively to samples before HCF tests. Compared with the fatigue life of standard heat treatment state sample, the fatigue life of samples after OTT at 1150 °C and 1180 °C, as well as samples after CD, has been improved, while the fatigue life of sample after OTT at 1200 °C has significantly decreased. After OTT at 1150 °C and 1180 °C, a portion of γ′ precipitates connected to form strip-shaped structures, and dislocation networks accumulated at the γ/γ′ interface slowed down the dissolution of γ′ phase. Under the creep stress, γ′ forms raft structure, with a large number of dense dislocation networks accumulating at the interface between matrix and the γ′ phase. The dislocation network hinders the alternating slip of fatigue dislocations in the matrix, reduces the formation of entangled dislocations, resulting in delayed crack initiation and propagation, and prolonged the fatigue life of the alloy. The dense raft structures formed after creep can also effectively hinder crack initiation. For the condition of OTT at 1200 °C, γ′ phase dissolved rapidly, accompanied with the precipitation of a large amount of secondary γ′ phase and the degradation of dislocation networks, which is the main factor leading to the decrease in fatigue life.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149768"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-09DOI: 10.1016/j.msea.2026.149761
Özer Zeybek , Casim Yazici , Abdulhadi Koşatepe , Fatih Mehmet Özkal , Gabriel Okon Ubana , Yasin Onuralp Özkılıç
The use of aluminum alloys in transport, aerospace, and structural applications continues to grow due to their exceptional strength to weight ratio, corrosion resistance, and formability. Nonetheless, as a result of their post-fire performance, aluminum alloys pose a higher risk to structural safety. Consequently, to assess these risks, a combined experimental and analytical study was carried out. The experimental program consisted of tensile tests on 31 coupons. These coupons were then subjected to fire-simulated temperatures of up to 550 °C with subsequent cooling to room temperature via water, natural air, and foam cooling. In the analytical phase, the response of AA6061-T651 to other properties such as yield strength, ultimate tensile strength, hardness, and elastic modulus based on temperature was integrated into a new set of empirical expressions. These models were compared with the experimental data which are available in the literature. The proposed models allow a generalized framework to be created in evaluating the post-fire performance of the 6xxx series aluminum alloys, which can be used for structural safety assessments and fire-resistant designs. Microstructural investigations confirmed that no new phase transformations occurred after fire exposure, while SEM and EDS analyses revealed grain coarsening, precipitate coarsening/dissolution, and recrystallization at temperatures above 300 °C.
{"title":"Residual mechanical performance and microstructural changes of 6061-T651 aluminum alloy after fire","authors":"Özer Zeybek , Casim Yazici , Abdulhadi Koşatepe , Fatih Mehmet Özkal , Gabriel Okon Ubana , Yasin Onuralp Özkılıç","doi":"10.1016/j.msea.2026.149761","DOIUrl":"10.1016/j.msea.2026.149761","url":null,"abstract":"<div><div>The use of aluminum alloys in transport, aerospace, and structural applications continues to grow due to their exceptional strength to weight ratio, corrosion resistance, and formability. Nonetheless, as a result of their post-fire performance, aluminum alloys pose a higher risk to structural safety. Consequently, to assess these risks, a combined experimental and analytical study was carried out. The experimental program consisted of tensile tests on 31 coupons. These coupons were then subjected to fire-simulated temperatures of up to 550 °C with subsequent cooling to room temperature via water, natural air, and foam cooling. In the analytical phase, the response of AA6061-T651 to other properties such as yield strength, ultimate tensile strength, hardness, and elastic modulus based on temperature was integrated into a new set of empirical expressions. These models were compared with the experimental data which are available in the literature. The proposed models allow a generalized framework to be created in evaluating the post-fire performance of the 6xxx series aluminum alloys, which can be used for structural safety assessments and fire-resistant designs. Microstructural investigations confirmed that no new phase transformations occurred after fire exposure, while SEM and EDS analyses revealed grain coarsening, precipitate coarsening/dissolution, and recrystallization at temperatures above 300 °C.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149761"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145973536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-09DOI: 10.1016/j.msea.2026.149735
Yunfeng Hu , Mojia Li , Jiaheng Li , Yahui Wu , Ran Ni , Yingbo Zhang , Dongdi Yin , Ying Zeng , Hui Chen
The common strength-ductility trade-off in precipitation-hardened Al-Zn-Mg-Cu alloys has restricted their application in critical load-bearing structures. This study introduces a hybrid processing strategy combining semi-solid isothermal treatment (SSIT), hot extrusion, and Zr/Y microalloying to achieve synergistic control of multi-scale particles and heterogeneous structures. SSIT refines micron-sized low-melting-point Mg(Zn,Cu,Al)2 eutectic phases into nanoscale lamellae (55 ± 10 nm thick), which fragment into submicron particles during extrusion, enhancing solute supersaturation (lattice expansion = 0.0004 Å) and promoting high-density precipitation. Multi-scale spheroidized Al8Cu4Y particles (ranging from 60 nm to 2.99 μm), together with a bimodal grain structure, suppress recrystallization and promote dislocation accumulation. precipitates at subgrain boundaries (∼15 nm) and intra-grain (∼4.52 nm) induce strain gradient hardening, thereby optimizing work hardening capacity. The T6-tempered alloy attains exceptional synergy, achieving an ultimate tensile strength of 794 MPa and an elongation of 8.7 %, outperforming the conventionally processed counterpart (704 MPa, 5.5 %). This strategy offers a promising pathway for overcoming the ultra-strength-ductility bottleneck in high-strength aluminum alloys.
{"title":"Tailoring multi-scale particles for synergistic high-strength and ductile in an Al-Zn-Mg-Cu-Zr-Y Alloy","authors":"Yunfeng Hu , Mojia Li , Jiaheng Li , Yahui Wu , Ran Ni , Yingbo Zhang , Dongdi Yin , Ying Zeng , Hui Chen","doi":"10.1016/j.msea.2026.149735","DOIUrl":"10.1016/j.msea.2026.149735","url":null,"abstract":"<div><div>The common strength-ductility trade-off in precipitation-hardened Al-Zn-Mg-Cu alloys has restricted their application in critical load-bearing structures. This study introduces a hybrid processing strategy combining semi-solid isothermal treatment (SSIT), hot extrusion, and Zr/Y microalloying to achieve synergistic control of multi-scale particles and heterogeneous structures. SSIT refines micron-sized low-melting-point Mg(Zn,Cu,Al)<sub>2</sub> eutectic phases into nanoscale lamellae (55 ± 10 nm thick), which fragment into submicron particles during extrusion, enhancing solute supersaturation (lattice expansion <span><math><mrow><mo>Δ</mo><mi>a</mi></mrow></math></span> = 0.0004 Å) and promoting high-density <span><math><mrow><msup><mi>η</mi><mo>′</mo></msup></mrow></math></span> precipitation. Multi-scale spheroidized Al<sub>8</sub>Cu<sub>4</sub>Y particles (ranging from 60 nm to 2.99 μm), together with a bimodal grain structure, suppress recrystallization and promote dislocation accumulation. <span><math><mrow><msup><mi>η</mi><mo>′</mo></msup></mrow></math></span> precipitates at subgrain boundaries (∼15 nm) and intra-grain (∼4.52 nm) induce strain gradient hardening, thereby optimizing work hardening capacity. The T6-tempered alloy attains exceptional synergy, achieving an ultimate tensile strength of 794 MPa and an elongation of 8.7 %, outperforming the conventionally processed counterpart (704 MPa, 5.5 %). This strategy offers a promising pathway for overcoming the ultra-strength-ductility bottleneck in high-strength aluminum alloys.</div></div>","PeriodicalId":385,"journal":{"name":"Materials Science and Engineering: A","volume":"953 ","pages":"Article 149735"},"PeriodicalIF":7.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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