In this study, austenitic low-density steels with 0, 1, and 3 wt% Cu additions were subjected to various solid-solution and aging treatments to examine their microstructural evolution and mechanical properties. After solution treatment at 950–1050 °C, all steels exhibited a single-phase austenitic structure. The addition of 3 wt% Cu caused the austenite softening, but it could effectively inhibit grain growth during the increase of solution treatment temperature, thereby enhancing grain boundary strengthening. In the aged state, high-density intragranular κ-carbides precipitated in all steels, while only a small amount of intergranular Cu-rich particles was observed in the Cu-containing steels. Furthermore, the addition of 3 wt% Cu promoted the formation and growth of κ-carbides, leading to an enhanced precipitation strengthening and a significant improvement in strength. The predominant deformation mechanism was dislocation glide in all steels. Strain hardening was attributed to dynamic slip band refinement, and Cu alloying contributed to reducing the spacing of slip bands. As a result, the Cu-containing steels achieved a higher work hardening rate and greater fracture elongation.
{"title":"Effect of Cu addition on the microstructure and the mechanical properties of austenitic low-density steel","authors":"Chuguang Tong , Chunguang Shen , Lingling Zhang , Yu Qi , Chi Zhang , Shijian Zheng","doi":"10.1016/j.matchar.2026.116185","DOIUrl":"10.1016/j.matchar.2026.116185","url":null,"abstract":"<div><div>In this study, austenitic low-density steels with 0, 1, and 3 wt% Cu additions were subjected to various solid-solution and aging treatments to examine their microstructural evolution and mechanical properties. After solution treatment at 950–1050 °C, all steels exhibited a single-phase austenitic structure. The addition of 3 wt% Cu caused the austenite softening, but it could effectively inhibit grain growth during the increase of solution treatment temperature, thereby enhancing grain boundary strengthening. In the aged state, high-density intragranular κ-carbides precipitated in all steels, while only a small amount of intergranular Cu-rich particles was observed in the Cu-containing steels. Furthermore, the addition of 3 wt% Cu promoted the formation and growth of κ-carbides, leading to an enhanced precipitation strengthening and a significant improvement in strength. The predominant deformation mechanism was dislocation glide in all steels. Strain hardening was attributed to dynamic slip band refinement, and Cu alloying contributed to reducing the spacing of slip bands. As a result, the Cu-containing steels achieved a higher work hardening rate and greater fracture elongation.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116185"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386601","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 : 2026-04-01Epub Date: 2026-03-09DOI: 10.1016/j.matchar.2026.116226
Pengtao Li , Chenke Ding , Yutong Song , Yihui Jiang , Fei Cao , Yanfang Wang , Zhongyi Ding , Yuanxi Liu , Ruihan Zhang , Yong Gao
High-strength high-conductivity (HSHC) copper alloys are urgently needed for cryogenic applications such as superconducting cables and pulsed magnets operating at liquid-nitrogen temperature and below. By integrating large-scale molecular dynamics simulations containing 472,689 datasets with interpretable machine learning, we reveal that detwinning-induced grain boundary migration rather than conventional dislocation - twin boundary interactions dominate plastic deformation below 150 K in nano-twinned Cu-18 wt% Ag alloys. Cryorolling followed by low-temperature annealing produces dense nanotwins with mean spacing of 5.2 nm, as confirmed by TEM. Atomistic simulations show that Ag segregation dramatically reduces the critical detwinning stress from 800 MPa (pure Cu) to 220 MPa, resulting in a pronounced Hall-Petch plateau below λ = 7.0 nm. SHAP analysis quantitatively demonstrates that detwinning accounts for >72% of plastic strain at T < 150 K. A random forest-derived (R2 = 99.4%) temperature–twin spacing phase diagram identifies a cryogenic service window (T < 150 K, λ = 3.0–12.0 nm) where flow stress stabilizes at 5.1 ± 0.2 GPa. These findings provide explicit design guidelines for next-generation HSHC copper alloys in extreme cryogenic environments.
{"title":"Machine learning-guided revelation of Detwinning-dominated cryogenic plasticity in Nano-twinned Cu-Ag alloys","authors":"Pengtao Li , Chenke Ding , Yutong Song , Yihui Jiang , Fei Cao , Yanfang Wang , Zhongyi Ding , Yuanxi Liu , Ruihan Zhang , Yong Gao","doi":"10.1016/j.matchar.2026.116226","DOIUrl":"10.1016/j.matchar.2026.116226","url":null,"abstract":"<div><div>High-strength high-conductivity (HSHC) copper alloys are urgently needed for cryogenic applications such as superconducting cables and pulsed magnets operating at liquid-nitrogen temperature and below. By integrating large-scale molecular dynamics simulations containing 472,689 datasets with interpretable machine learning, we reveal that detwinning-induced grain boundary migration rather than conventional dislocation - twin boundary interactions dominate plastic deformation below 150 K in nano-twinned Cu-18 wt% Ag alloys. Cryorolling followed by low-temperature annealing produces dense nanotwins with mean spacing of 5.2 nm, as confirmed by TEM. Atomistic simulations show that Ag segregation dramatically reduces the critical detwinning stress from 800 MPa (pure Cu) to 220 MPa, resulting in a pronounced Hall-Petch plateau below λ = 7.0 nm. SHAP analysis quantitatively demonstrates that detwinning accounts for >72% of plastic strain at <em>T</em> < 150 K. A random forest-derived (R<sup>2</sup> = 99.4%) temperature–twin spacing phase diagram identifies a cryogenic service window (T < 150 K, λ = 3.0–12.0 nm) where flow stress stabilizes at 5.1 ± 0.2 GPa. These findings provide explicit design guidelines for next-generation HSHC copper alloys in extreme cryogenic environments.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116226"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386689","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 : 2026-04-01Epub Date: 2026-03-02DOI: 10.1016/j.matchar.2026.116139
A.M.L. Andersson, R.F.L. Mellor, J.M. Hogg, H.C. Cole, G.I. Lampronti, N.L. Church, O.S. Houghton, N.G. Jones, H.J. Stone
Ti-Fe-Al and Ti-Fe-Mo alloys containing B2 superlattice precipitates within an A2 matrix have attracted interest for structural applications. However, few studies have considered alloys derived from the quaternary Ti-Fe-Mo-Al system. In this work, six Ti-Fe-Mo-Al compositions with 70 at.% Ti have been aged for 1000 h at , , and 1000 °C to assess their equilibrium phases. A2+B2 phase microstructures formed in two of the alloys considered: Ti-20Fe-5Mo-5Al at both and 1000 °C, and Ti-15Fe-10Mo-5Al at 800 °C. A2+B2 microstructures were not observed in the other alloys investigated. At high temperatures, most alloys were single-phase A2, while at lower temperatures A3 and D019 phases were widely observed.
Studying continuous cooling of Ti-20Fe-5Mo-5Al from the solid solution showed a change in precipitation behaviour with cooling rate. Intermediate cooling rates permitted discontinuous B2 precipitation. The slowest cooling rate led to continuous B2 precipitation and the observation of the D8 G-phase. This transition in precipitation mechanism was attributed to the relative rates of bulk and grain boundary diffusion at varying temperatures.
{"title":"Superlattice phase precipitation in Ti-Fe-Mo-Al alloys","authors":"A.M.L. Andersson, R.F.L. Mellor, J.M. Hogg, H.C. Cole, G.I. Lampronti, N.L. Church, O.S. Houghton, N.G. Jones, H.J. Stone","doi":"10.1016/j.matchar.2026.116139","DOIUrl":"10.1016/j.matchar.2026.116139","url":null,"abstract":"<div><div>Ti-Fe-Al and Ti-Fe-Mo alloys containing B2 superlattice precipitates within an A2 matrix have attracted interest for structural applications. However, few studies have considered alloys derived from the quaternary Ti-Fe-Mo-Al system. In this work, six Ti-Fe-Mo-Al compositions with 70<!--> <!-->at.% Ti have been aged for 1000<!--> <!-->h at <span><math><mrow><mn>600</mn></mrow></math></span>, <span><math><mrow><mn>800</mn></mrow></math></span>, and 1000<!--> <!-->°C to assess their equilibrium phases. A2+B2 phase microstructures formed in two of the alloys considered: Ti-20Fe-5Mo-5Al at both <span><math><mrow><mn>800</mn></mrow></math></span> <!--> <!-->and 1000<!--> <!-->°C, and Ti-15Fe-10Mo-5Al at 800<!--> <!-->°C. A2+B2 microstructures were not observed in the other alloys investigated. At high temperatures, most alloys were single-phase A2, while at lower temperatures A3 and D0<sub>19</sub> phases were widely observed.</div><div>Studying continuous cooling of Ti-20Fe-5Mo-5Al from the solid solution showed a change in precipitation behaviour with cooling rate. Intermediate cooling rates permitted discontinuous B2 precipitation. The slowest cooling rate led to continuous B2 precipitation and the observation of the D8<span><math><msub><mrow></mrow><mrow><mtext>a</mtext></mrow></msub></math></span> G-phase. This transition in precipitation mechanism was attributed to the relative rates of bulk and grain boundary diffusion at varying temperatures.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116139"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386695","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 : 2026-04-01Epub Date: 2026-03-08DOI: 10.1016/j.matchar.2026.116231
Ranpeng Lu , Yu Pan , Yanjun Liu , Jiayu Li , Xinjing Wang , Peng Yu , Xin Lu
The trade-off dilemma between fine grain and residual pore has been a challenge in powder metallurgy (PM) titanium (Ti) alloys via pressureless sintering, since the grain growth and densification are both thermally activated. The fabrication of the fine equiaxed-grained Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy with high density is hereby addressed by regulating the grain growth behavior. Results show that an obvious transition in grain boundary migration occurs with the decrease of sintering temperature from 1200 °C to 1050 °C, leading to a nearly three-fold rise in grain boundary migration activation enthalpy Ea and an almost 103-fold suppression in grain boundary mobility Mb. The underlying balance in the trade-off dilemma is uncovered in the optimized refined equiaxed-grain and its advantageous densification by grain boundary diffusion, which produces an average grain size of 16.4 ± 0.5 μm and a relative density of 99.1 ± 0.3%. During plastic deformation, the refined equiaxed-grain provides high level of stress to activate the <c+a> dislocations, disperses the local stress and suppresses the crack propagation, avoiding the premature failure. Accordingly, the fabricated TA15–1050 sample with fine equiaxed-grain and high density exhibits unprecedented room-temperature tensile properties, with the ultimate tensile strength (UTS) of 1053 MPa and elongation (EL) of 17.5%. These values significantly exceed the ASTM B381 for Ti-6Al-4V (TC4) alloy, the GB/T 2965–2023 for TA15 alloy and other pressureless sintered PM Ti alloys reported thus far. This work proposes a cost-effective strategy to fabricate the favorable microstructure with excellent mechanical properties via pressureless sintering.
{"title":"A high-performance MIM TA15 alloy scheme: breaking through the trade-off dilemma between fine grain and residual pore in pressureless sintering","authors":"Ranpeng Lu , Yu Pan , Yanjun Liu , Jiayu Li , Xinjing Wang , Peng Yu , Xin Lu","doi":"10.1016/j.matchar.2026.116231","DOIUrl":"10.1016/j.matchar.2026.116231","url":null,"abstract":"<div><div>The trade-off dilemma between fine grain and residual pore has been a challenge in powder metallurgy (PM) titanium (Ti) alloys via pressureless sintering, since the grain growth and densification are both thermally activated. The fabrication of the fine equiaxed-grained Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy with high density is hereby addressed by regulating the grain growth behavior. Results show that an obvious transition in grain boundary migration occurs with the decrease of sintering temperature from 1200 °C to 1050 °C, leading to a nearly three-fold rise in grain boundary migration activation enthalpy <em>E</em><sub><em>a</em></sub> and an almost 10<sup>3</sup>-fold suppression in grain boundary mobility <em>M</em><sub><em>b</em></sub>. The underlying balance in the trade-off dilemma is uncovered in the optimized refined equiaxed-grain and its advantageous densification by grain boundary diffusion, which produces an average grain size of 16.4 ± 0.5 μm and a relative density of 99.1 ± 0.3%. During plastic deformation, the refined equiaxed-grain provides high level of stress to activate the <strong><em><c</em></strong> <strong><em>+</em></strong> <strong><em>a></em></strong> dislocations, disperses the local stress and suppresses the crack propagation, avoiding the premature failure. Accordingly, the fabricated TA15–1050 sample with fine equiaxed-grain and high density exhibits unprecedented room-temperature tensile properties, with the ultimate tensile strength (UTS) of 1053 MPa and elongation (EL) of 17.5%. These values significantly exceed the ASTM B381 for Ti-6Al-4V (TC4) alloy, the GB/T 2965–2023 for TA15 alloy and other pressureless sintered PM Ti alloys reported thus far. This work proposes a cost-effective strategy to fabricate the favorable microstructure with excellent mechanical properties via pressureless sintering.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116231"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386688","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 : 2026-04-01Epub Date: 2026-03-06DOI: 10.1016/j.matchar.2026.116229
Yeonggeun Cho , Hyung-Jun Cho , Han-Seop Noh , Sung-Joon Kim
The precipitation behavior of Nb-containing precipitates was systematically investigated in Nb-added AISI 301LN stainless steel during hot rolling, intermediate annealing, cold rolling, and final annealing treatment. During hot rolling, Z-phase (NbCrN) and NbN precipitates were preferentially formed along the rolling direction. The formation of these precipitates was promoted by increasing Nb content, while they largely remained undissolved during intermediate annealing treatment owing to their high thermal stability. Cold rolling fragmented coarse precipitates and introduced a high density of defects, thereby increasing the number of favorable nucleation sites for subsequent precipitation. After final annealing treatment, numerous nanoscale precipitates were observed, identified as Z-phase and NbN by chemical and crystallographic indexing. These precipitates exhibited various morphologies including rectangular and spherical shapes, influenced by previous thermo-mechanical process. Quantitative analysis revealed a modest change in the weight fraction of Nb-containing precipitates between hot rolling and cold rolling, followed by a substantial increase after final annealing. Z-phase was consistently identified as the dominant precipitate throughout all processing steps, and its formation appeared to proceed via transformation from pre-existing NbN.
{"title":"Evolution of NbN and Z-phase transformation during thermo-mechanical process of Nb-containing AISI 301LN stainless steel","authors":"Yeonggeun Cho , Hyung-Jun Cho , Han-Seop Noh , Sung-Joon Kim","doi":"10.1016/j.matchar.2026.116229","DOIUrl":"10.1016/j.matchar.2026.116229","url":null,"abstract":"<div><div>The precipitation behavior of Nb-containing precipitates was systematically investigated in Nb-added AISI 301LN stainless steel during hot rolling, intermediate annealing, cold rolling, and final annealing treatment. During hot rolling, <em>Z</em>-phase (NbCrN) and NbN precipitates were preferentially formed along the rolling direction. The formation of these precipitates was promoted by increasing Nb content, while they largely remained undissolved during intermediate annealing treatment owing to their high thermal stability. Cold rolling fragmented coarse precipitates and introduced a high density of defects, thereby increasing the number of favorable nucleation sites for subsequent precipitation. After final annealing treatment, numerous nanoscale precipitates were observed, identified as <em>Z</em>-phase and NbN by chemical and crystallographic indexing. These precipitates exhibited various morphologies including rectangular and spherical shapes, influenced by previous thermo-mechanical process. Quantitative analysis revealed a modest change in the weight fraction of Nb-containing precipitates between hot rolling and cold rolling, followed by a substantial increase after final annealing. <em>Z</em>-phase was consistently identified as the dominant precipitate throughout all processing steps, and its formation appeared to proceed via transformation from pre-existing NbN.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116229"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386748","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 : 2026-04-01Epub Date: 2026-03-06DOI: 10.1016/j.matchar.2026.116208
J.P. Hu, G.Q. Huang, T. Sun, J. Xu, Z.H. Wang, X.M. Feng, Y.F. Shen
Additive manufacturing of fully-dense, fine-grained equiatomic CoCrFeNiMn high-entropy alloy (HEA) with exceptional cryogenic mechanical properties is of great scientific and industrial interest, yet remains highly challenging. Herein, we successfully fabricated large-scale, three-dimensional, fine-grained CoCrFeNiMn HEA component using friction stir additive manufacturing (FSAM), achieving significantly enhanced mechanical performance. The microstructure, mechanical behavior from room temperature to cryogenic conditions, and fracture characteristics of the FSAM component were systematically examined. The results reveal that FSAM-induced severe thermoplastic deformation markedly refines the grains, achieving an average grain size much smaller than that of the base material (BM). Moreover, the repeated thermal cycling along the build direction induces a gradient microstructure, characterized by increased grain size and decreased dislocation density from the top to the bottom regions. Fracture analyses reveal that dislocation–twin interactions govern the dominant failure mechanisms at both 298 K and 77 K, contributing to the superior strength of the FSAM component compared with the BM. Specifically, the yield strength (YS) increases by 42% to 470 MPa at 298 K and by 27% to 752 MPa at 77 K, while the ultimate tensile strength (UTS) rises by 17% to 617 MPa and by 8.5% to 1092 MPa, respectively. Although ductility is somewhat reduced, an excellent strength–ductility balance is maintained. These results establish FSAM as a viable pathway for producing bulk CoCrFeNiMn HEA component and potentially extendable to other FCC-based medium- and high-entropy alloy systems for demanding cryogenic applications.
{"title":"Unveiling microstructure characteristics and cryogenic mechanical properties of friction stir additive manufactured CoCrFeNiMn high-entropy alloy","authors":"J.P. Hu, G.Q. Huang, T. Sun, J. Xu, Z.H. Wang, X.M. Feng, Y.F. Shen","doi":"10.1016/j.matchar.2026.116208","DOIUrl":"10.1016/j.matchar.2026.116208","url":null,"abstract":"<div><div>Additive manufacturing of fully-dense, fine-grained equiatomic CoCrFeNiMn high-entropy alloy (HEA) with exceptional cryogenic mechanical properties is of great scientific and industrial interest, yet remains highly challenging. Herein, we successfully fabricated large-scale, three-dimensional, fine-grained CoCrFeNiMn HEA component using friction stir additive manufacturing (FSAM), achieving significantly enhanced mechanical performance. The microstructure, mechanical behavior from room temperature to cryogenic conditions, and fracture characteristics of the FSAM component were systematically examined. The results reveal that FSAM-induced severe thermoplastic deformation markedly refines the grains, achieving an average grain size much smaller than that of the base material (BM). Moreover, the repeated thermal cycling along the build direction induces a gradient microstructure, characterized by increased grain size and decreased dislocation density from the top to the bottom regions. Fracture analyses reveal that dislocation–twin interactions govern the dominant failure mechanisms at both 298 K and 77 K, contributing to the superior strength of the FSAM component compared with the BM. Specifically, the yield strength (YS) increases by 42% to 470 MPa at 298 K and by 27% to 752 MPa at 77 K, while the ultimate tensile strength (UTS) rises by 17% to 617 MPa and by 8.5% to 1092 MPa, respectively. Although ductility is somewhat reduced, an excellent strength–ductility balance is maintained. These results establish FSAM as a viable pathway for producing bulk CoCrFeNiMn HEA component and potentially extendable to other FCC-based medium- and high-entropy alloy systems for demanding cryogenic applications.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116208"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386750","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 : 2026-04-01Epub Date: 2026-02-18DOI: 10.1016/j.matchar.2026.116169
Yuanpeng Yang , Chang Liu , Jiasheng Dong , Langhong Lou
In this study, σ phase precipitation and dissolution behavior during long-term aging at 900 °C were systematically investigated in a Cr-rich polycrystalline Ni-based superalloy. Multiscale characterization reveals that Cr and W segregation drives the preferential precipitation of lath-like σ phase in the γ matrix. With prolonged aging, σ phase increasingly nucleates at M23C6 carbide interface and grows into the γ matrix. Atomic-scale analysis demonstrates a highly coherent M23C6/σ nucleation interface established through long-range atomic matching. While the σ/γ growth interface adopts a stepped configuration to minimize lattice strain, further facilitated by internal planar defects. During later-stage aging, σ phase dissolution is dominated by competitive consumption of Cr due to substantial M23C6 precipitation. Furthermore, mechanical tests indicates that the limited fraction of σ phase leads to a negligible effect on stress-rupture life at 900 °C/200 MPa. This work provides insights into the interfacial mechanisms of σ phase precipitation and the competitive kinetics governing its dissolution, thereby enhancing the understanding of microstructural stability in such alloys.
{"title":"Mechanisms of σ phase precipitation and dissolution behavior in a Cr-rich Ni-based superalloy during long-term aging","authors":"Yuanpeng Yang , Chang Liu , Jiasheng Dong , Langhong Lou","doi":"10.1016/j.matchar.2026.116169","DOIUrl":"10.1016/j.matchar.2026.116169","url":null,"abstract":"<div><div>In this study, σ phase precipitation and dissolution behavior during long-term aging at 900 °C were systematically investigated in a Cr-rich polycrystalline Ni-based superalloy. Multiscale characterization reveals that Cr and W segregation drives the preferential precipitation of lath-like σ phase in the γ matrix. With prolonged aging, σ phase increasingly nucleates at M<sub>23</sub>C<sub>6</sub> carbide interface and grows into the γ matrix. Atomic-scale analysis demonstrates a highly coherent M<sub>23</sub>C<sub>6</sub><strong>/</strong>σ nucleation interface established through long-range atomic matching. While the σ/γ growth interface adopts a stepped configuration to minimize lattice strain, further facilitated by internal planar defects. During later-stage aging, σ phase dissolution is dominated by competitive consumption of Cr due to substantial M<sub>23</sub>C<sub>6</sub> precipitation. Furthermore, mechanical tests indicates that the limited fraction of σ phase leads to a negligible effect on stress-rupture life at 900 °C/200 MPa. This work provides insights into the interfacial mechanisms of σ phase precipitation and the competitive kinetics governing its dissolution, thereby enhancing the understanding of microstructural stability in such alloys.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116169"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386465","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 : 2026-04-01Epub Date: 2026-02-23DOI: 10.1016/j.matchar.2026.116193
Ming Li , Xiaojie Zhou , Xu Wang , Shengxiong Tang , Yuanchun Huang , Yongcheng Lin , Jiang Zhang , Xianzheng Lu , Xiaomin Chen
The deformation mechanisms of coarse and fine grains in a bimodal-structured Mg-Gd-Y-Zn-Zr alloy and its influence on work hardening and fracture behavior were systematically investigated through in-situ EBSD tensile test at room temperature. Quantitative analysis of slip traces revealed that fine grains with random orientations accommodated plastic strain through basal <a > dislocation slip and grain rotation in deformation stage I (0%–4%). In subsequent deformation stage II (4%–10%), coarse grains with basal orientation accommodated plastic strain through prismatic <a > dislocation slip. In the later stage of plastic deformation, the heterogeneous deformation-induced (HDI) stress at the coarse/fine grain interface promoted the activation of additional non-basal dislocation slip. The improved Hall-Petch relationship, combined with Schmid factor analysis, demonstrated that coarse grains can improve the yield strength of bimodal-structured alloy due to the synergistic contributions of strong basal texture and intragranular lamellar LPSO phases. The heterogeneous deformation between coarse and fine grains induces significant back stress and activates multiple dislocation slip modes, which together enhance work hardening capacity and suppress strain localization. The coarse grains also exhibit crack blunting and deflection effects that effectively impede crack propagation, increase energy absorption during fracture, and delay final failure. These findings provide valuable insights for the microstructural design of bimodal-structured magnesium alloys.
{"title":"Influence of deformation mechanisms in coarse and fine grains on the work hardening and fracture behavior of a bimodal-structured Mg-Gd-Y-Zn-Zr alloy","authors":"Ming Li , Xiaojie Zhou , Xu Wang , Shengxiong Tang , Yuanchun Huang , Yongcheng Lin , Jiang Zhang , Xianzheng Lu , Xiaomin Chen","doi":"10.1016/j.matchar.2026.116193","DOIUrl":"10.1016/j.matchar.2026.116193","url":null,"abstract":"<div><div>The deformation mechanisms of coarse and fine grains in a bimodal-structured Mg-Gd-Y-Zn-Zr alloy and its influence on work hardening and fracture behavior were systematically investigated through in-situ EBSD tensile test at room temperature. Quantitative analysis of slip traces revealed that fine grains with random orientations accommodated plastic strain through basal <a > dislocation slip and grain rotation in deformation stage I (0%–4%). In subsequent deformation stage II (4%–10%), coarse grains with basal orientation accommodated plastic strain through prismatic <a > dislocation slip. In the later stage of plastic deformation, the heterogeneous deformation-induced (HDI) stress at the coarse/fine grain interface promoted the activation of additional non-basal dislocation slip. The improved Hall-Petch relationship, combined with Schmid factor analysis, demonstrated that coarse grains can improve the yield strength of bimodal-structured alloy due to the synergistic contributions of strong basal texture and intragranular lamellar LPSO phases. The heterogeneous deformation between coarse and fine grains induces significant back stress and activates multiple dislocation slip modes, which together enhance work hardening capacity and suppress strain localization. The coarse grains also exhibit crack blunting and deflection effects that effectively impede crack propagation, increase energy absorption during fracture, and delay final failure. These findings provide valuable insights for the microstructural design of bimodal-structured magnesium alloys.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116193"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386575","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 : 2026-04-01Epub Date: 2026-02-09DOI: 10.1016/j.matchar.2026.116147
Yuliang Zhao , Weixiang He , G. González-Doncel , R. Fernández
The load transfer mechanism during tensile deformation of an Al-Cu-Fe alloy is analysed on the basis of in-situ synchrotron radiation X-ray diffraction data. The alloy was specifically fabricated with a high Fe content to simulate recycled Al alloy. The final aim of the study is to explore the potential of using recycled alloys for structural application. As is well known, recycled Al alloys are characterized by a high amount of Fe content, which is usually detrimental to their mechanical properties. However, microstructural modification through friction stir processing (FSP) has emerged as a promising approach to address this issue. The relevance of the load transfer mechanism after FSP is shown to be outstandingly manifested during the onset of plastic deformation. It is proposed that this mechanism accounts for a well adhered interface between the Al matrix and the Cu- and Fe-rich particles. For comparative purposes the in-situ synchrotron X-ray diffraction measurements were conducted on, both, the as-processed alloy (initial) microstructure as well as FSPed microstructure. As anticipated, relevant findings regarding the load transfer mechanisms are derived from the study in both conditions.
{"title":"Analysis of the load distribution in a Fe-rich aluminum alloy during tensile deformation using synchrotron X-ray diffraction","authors":"Yuliang Zhao , Weixiang He , G. González-Doncel , R. Fernández","doi":"10.1016/j.matchar.2026.116147","DOIUrl":"10.1016/j.matchar.2026.116147","url":null,"abstract":"<div><div>The load transfer mechanism during tensile deformation of an Al-Cu-Fe alloy is analysed on the basis of <em>in-situ</em> synchrotron radiation X-ray diffraction data. The alloy was specifically fabricated with a high Fe content to simulate recycled Al alloy. The final aim of the study is to explore the potential of using recycled alloys for structural application. As is well known, recycled Al alloys are characterized by a high amount of Fe content, which is usually detrimental to their mechanical properties. However, microstructural modification through friction stir processing (FSP) has emerged as a promising approach to address this issue. The relevance of the load transfer mechanism after FSP is shown to be outstandingly manifested during the onset of plastic deformation. It is proposed that this mechanism accounts for a well adhered interface between the Al matrix and the Cu- and Fe-rich particles. For comparative purposes the <em>in-situ</em> synchrotron X-ray diffraction measurements were conducted on, both, the as-processed alloy (initial) microstructure as well as FSPed microstructure. As anticipated, relevant findings regarding the load transfer mechanisms are derived from the study in both conditions.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116147"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146196840","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 : 2026-04-01Epub Date: 2026-02-24DOI: 10.1016/j.matchar.2026.116197
Guili Xu , Zhiqiang Wu , Peng Huang , Jun Hu , Yihan Zhou , Guoyin Zu
This study systematically investigated the effect of deep cryogenic treatment (DCT) on the microstructural evolution and fracture toughness of M2 high-speed steel (HSS), with particular emphasis on the critical role of microstructural variations in crack initiation and propagation behavior. The results revealed that DCT promoted the transformation of unstable retained austenite, significantly increased the density of martensitic boundaries through substructure refinement, and promoted the uniform dispersion of carbides, thereby improving the fracture toughness by 33.8%. Although DCT did not alter the crack initiation sites, it had a pronounced influence on crack propagation behavior. In the conventionally treated specimen, cracks propagated smoothly along prior austenite boundaries or directly through primary carbides. The DCT specimen exhibited frequent crack deflection, blunting, and branching, owing to the refinement of martensitic variant units, the increased density of martensitic block boundaries, and the uniform dispersion of fine carbides. Furthermore, the refinement of martensite decreased the Schmid factor and enhanced its spatial heterogeneity near the crack path, thereby suppressing the activation of favorable slip systems and promoting heterogeneous strain partitioning. Consequently, the formation of dislocation shielding zones ahead of the crack tip effectively reduced the local stress intensity factor and enhanced crack resistance. This study clarifies the mechanism of DCT-induced toughness enhancement in HSS and provides useful guidance for microstructural design and process optimization.
{"title":"Effect of deep cryogenic treatment on crack initiation and propagation behavior in M2 high-speed steel","authors":"Guili Xu , Zhiqiang Wu , Peng Huang , Jun Hu , Yihan Zhou , Guoyin Zu","doi":"10.1016/j.matchar.2026.116197","DOIUrl":"10.1016/j.matchar.2026.116197","url":null,"abstract":"<div><div>This study systematically investigated the effect of deep cryogenic treatment (DCT) on the microstructural evolution and fracture toughness of M2 high-speed steel (HSS), with particular emphasis on the critical role of microstructural variations in crack initiation and propagation behavior. The results revealed that DCT promoted the transformation of unstable retained austenite, significantly increased the density of martensitic boundaries through substructure refinement, and promoted the uniform dispersion of carbides, thereby improving the fracture toughness by 33.8%. Although DCT did not alter the crack initiation sites, it had a pronounced influence on crack propagation behavior. In the conventionally treated specimen, cracks propagated smoothly along prior austenite boundaries or directly through primary carbides. The DCT specimen exhibited frequent crack deflection, blunting, and branching, owing to the refinement of martensitic variant units, the increased density of martensitic block boundaries, and the uniform dispersion of fine carbides. Furthermore, the refinement of martensite decreased the Schmid factor and enhanced its spatial heterogeneity near the crack path, thereby suppressing the activation of favorable slip systems and promoting heterogeneous strain partitioning. Consequently, the formation of dislocation shielding zones ahead of the crack tip effectively reduced the local stress intensity factor and enhanced crack resistance. This study clarifies the mechanism of DCT-induced toughness enhancement in HSS and provides useful guidance for microstructural design and process optimization.</div></div>","PeriodicalId":18727,"journal":{"name":"Materials Characterization","volume":"234 ","pages":"Article 116197"},"PeriodicalIF":5.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147386694","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号