Pub Date : 2026-03-15DOI: 10.1016/j.actamat.2026.122127
Yandi Jia, Yingjie Ma, Rongpei Shi, Hao Wang, Kui Du, Yujing Yang, Qian Wang, Sensen Huang, Min Qi, Yingying Shen, Jinmin Liu, Jiafeng Lei, Rui Yang
The strength–ductility trade-off remains a central challenge in structural titanium alloys. While heterogeneous microstructure design is a promising solution, existing strategies rely on single metastable phase refinement. Here, we demonstrate a novel paradigm in a Ti-3Al-5Mo-4.5V (wt.%) alloy by synergistically activating dual metastable phase refinement pathways—ω-assisted α nucleation and α″ decomposition—for the first time. This approach successfully fabricates a four-scale heterogeneous α (FSH-α) microstructure, comprising micron-scale primary αp alongside three distinct secondary α morphologies: micron-scale αs-fine, nanoscale αs-ultra, and ladder-like αs-ladder. Advanced characterization reveals that αs-ultra forms via ω-assisted nucleation, while αs-fine and αs-ladder evolve from the decomposition of α″, with the latter originating from α″ with lattice distortion regions. Compared to the conventional annealed microstructure and two-scale heterogeneous α (TSH-α) microstructure refined solely through ω-assisted αs-ultra nucleation, the FSH-α structure exhibits a superior yield strength (990–1050 MPa vs. 820–850 MPa and 880–970 MPa) without sacrificing ductility (11–16% elongation vs. 12–15% and 14–18%). This enhancement stems from hetero-deformation induced (HDI) strengthening due to a multi-tiered network of hetero-interface, where plastically deformable αs-fine domains act as mechanical buffers, generating additional HDI stress while coordinating strain to maintain ductility. This work establishes a transformative strategy for designing hierarchical heterostructures by harnessing the synergy of multiple phase transformations to overcome property trade-offs in α + β titanium alloys.
{"title":"Four-scale Hierarchical α Microstructure via ω and α″ Synergistic Refinement: Overcoming Strength–Ductility Trade-off in an α + β Ti-alloy","authors":"Yandi Jia, Yingjie Ma, Rongpei Shi, Hao Wang, Kui Du, Yujing Yang, Qian Wang, Sensen Huang, Min Qi, Yingying Shen, Jinmin Liu, Jiafeng Lei, Rui Yang","doi":"10.1016/j.actamat.2026.122127","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122127","url":null,"abstract":"The strength–ductility trade-off remains a central challenge in structural titanium alloys. While heterogeneous microstructure design is a promising solution, existing strategies rely on single metastable phase refinement. Here, we demonstrate a novel paradigm in a Ti-3Al-5Mo-4.5V (wt.%) alloy by <ce:bold>synergistically activating dual metastable phase refinement pathways</ce:bold>—ω-assisted α nucleation and α″ decomposition—<ce:italic>for the first time</ce:italic>. This approach successfully fabricates a four-scale heterogeneous α (FSH-α) microstructure, comprising micron-scale primary α<ce:inf loc=\"post\">p</ce:inf> alongside three distinct secondary α morphologies: micron-scale α<ce:inf loc=\"post\">s-fine</ce:inf>, nanoscale α<ce:inf loc=\"post\">s-ultra</ce:inf>, and ladder-like α<ce:inf loc=\"post\">s-ladder</ce:inf>. Advanced characterization reveals that α<ce:inf loc=\"post\">s-ultra</ce:inf> forms via ω-assisted nucleation, while α<ce:inf loc=\"post\">s-fine</ce:inf> and α<ce:inf loc=\"post\">s-ladder</ce:inf> evolve from the decomposition of α″, with the latter originating from α″ with lattice distortion regions. Compared to the conventional annealed microstructure and two-scale heterogeneous α (TSH-α) microstructure refined solely through ω-assisted α<ce:inf loc=\"post\">s-ultra</ce:inf> nucleation, the FSH-α structure exhibits a superior yield strength (990–1050 MPa vs. 820–850 MPa and 880–970 MPa) without sacrificing ductility (11–16% elongation vs. 12–15% and 14–18%). This enhancement stems from hetero-deformation induced (HDI) strengthening due to a multi-tiered network of hetero-interface, where plastically deformable α<ce:inf loc=\"post\">s-fine</ce:inf> domains act as mechanical buffers, generating additional HDI stress while coordinating strain to maintain ductility. This work establishes a transformative strategy for designing hierarchical heterostructures by harnessing the synergy of multiple phase transformations to overcome property trade-offs in α + β titanium alloys.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"13 1","pages":"122127"},"PeriodicalIF":9.4,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-15DOI: 10.1016/j.actamat.2026.122130
Rei Yano, Masaki Tanaka, Shigeto Yamasaki, Tatsuya Morikawa, Tomohito Tsuru
In order to elucidate the influence of the athermal omega phase (ωath) and solute V on the thermally activated process of dislocation glide in β-titanium alloys of Ti–17V and Ti–22V, the values of effective shear stress, activation volume and activation enthalpy were obtained by tensile tests and strain-rate jump tests at various temperatures. Effective shear stresses showed a strong temperature dependence, indicating that yielding is controlled by a thermally activated process of dislocation glide. The temperature dependence of the activation enthalpy suggested that the process of overcoming the Peierls potential controls the dislocation glide below Ttrans, while interaction with ωath or solute V is possibly dominant above Ttrans. It was found that the shearing of ωath or the interaction with its coherent stress fields are unlikely to be dominant for the thermally activated process of dislocation glide, because the CRSS for the shearing of ωath is much smaller than the experimental value and the activation volumes estimated for the coherent stress fields are significantly larger than those obtained experimentally. Interaction with a single solute V atom is also unlikely to be dominant because the estimated activation volumes are significantly smaller than the experimentally evaluated values. The interaction between dislocation and several solute V atoms is expected to be reasonable for the thermally activated process for dislocation glide above Ttrans.
{"title":"Thermally activated process of dislocation glide in Ti–17V and Ti–22V alloys","authors":"Rei Yano, Masaki Tanaka, Shigeto Yamasaki, Tatsuya Morikawa, Tomohito Tsuru","doi":"10.1016/j.actamat.2026.122130","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122130","url":null,"abstract":"In order to elucidate the influence of the athermal omega phase (ω<ce:inf loc=\"post\">ath</ce:inf>) and solute V on the thermally activated process of dislocation glide in β-titanium alloys of Ti–17V and Ti–22V, the values of effective shear stress, activation volume and activation enthalpy were obtained by tensile tests and strain-rate jump tests at various temperatures. Effective shear stresses showed a strong temperature dependence, indicating that yielding is controlled by a thermally activated process of dislocation glide. The temperature dependence of the activation enthalpy suggested that the process of overcoming the Peierls potential controls the dislocation glide below <ce:italic>T</ce:italic><ce:inf loc=\"post\">trans</ce:inf>, while interaction with ω<ce:inf loc=\"post\">ath</ce:inf> or solute V is possibly dominant above <ce:italic>T</ce:italic><ce:inf loc=\"post\">trans</ce:inf>. It was found that the shearing of ω<ce:inf loc=\"post\">ath</ce:inf> or the interaction with its coherent stress fields are unlikely to be dominant for the thermally activated process of dislocation glide, because the CRSS for the shearing of ω<ce:inf loc=\"post\">ath</ce:inf> is much smaller than the experimental value and the activation volumes estimated for the coherent stress fields are significantly larger than those obtained experimentally. Interaction with a single solute V atom is also unlikely to be dominant because the estimated activation volumes are significantly smaller than the experimentally evaluated values. The interaction between dislocation and several solute V atoms is expected to be reasonable for the thermally activated process for dislocation glide above <ce:italic>T</ce:italic><ce:inf loc=\"post\">trans</ce:inf>.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"13 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2026-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147465314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mechanical field control in powder bed fusion is critical in mitigating distortion and cracking by reducing residual stresses, and enhancing mechanical properties by regulating dislocation structures. However, achieving these while preserving optimal melt region dimensions for desired build quality and microstructures remains challenging due to the inherent positive correlations among input energy, melt region and heat-affected zone (HAZ) dimensions, and residual stresses and strains. This study establishes a framework for effectively manipulating residual stresses and strains in melt region and HAZ, on the premise of preserving melt depth with error margins <8%. Through thermomechanical analyses and experimental validations, we investigate the effects of melting strategies and heat accumulation on residual stress–strain constitutive behaviors. Although conventional strategies such as shortening beam path length or spot melting are commonly employed to reduce residual stresses, we reveal their limited effectiveness under typical conditions where heat accumulates. In contrast, we propose the concept of equivalent infinite cooling time interval, based on which the real-spot (RS) melting strategy can significantly reduce macroscopic residual stresses. The underlying mechanisms are elucidated by revealing the dual effect of heat accumulation on residual stresses and strains, which induces a trade-off between their peak levels and total affected areas. Moreover, we demonstrate that the RS melting strategy alleviates continuous compressive plastic deformation in melt region and HAZ by reshaping principal plastic strain orientations and alternating compressive and tensile plastic strain components. This enables reducing residual stresses while increasing cumulative plastic strains, thereby overcoming the limitations in mechanical field control imposed by the positive correlation between residual stresses and strains.
{"title":"Mechanical Field Control in Electron Beam Powder Bed Fusion: Dual Effect of Heat Accumulation and Melting Strategies based on Equivalent Infinite Cooling Time Interval","authors":"Yuchao Lei, Yufan Zhao, Kenta Yamanaka, Yi Zhang, Xin Lin, Akihiko Chiba","doi":"10.1016/j.actamat.2026.122125","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122125","url":null,"abstract":"Mechanical field control in powder bed fusion is critical in mitigating distortion and cracking by reducing residual stresses, and enhancing mechanical properties by regulating dislocation structures. However, achieving these while preserving optimal melt region dimensions for desired build quality and microstructures remains challenging due to the inherent positive correlations among input energy, melt region and heat-affected zone (HAZ) dimensions, and residual stresses and strains. This study establishes a framework for effectively manipulating residual stresses and strains in melt region and HAZ, on the premise of preserving melt depth with error margins <8%. Through thermomechanical analyses and experimental validations, we investigate the effects of melting strategies and heat accumulation on residual stress–strain constitutive behaviors. Although conventional strategies such as shortening beam path length or spot melting are commonly employed to reduce residual stresses, we reveal their limited effectiveness under typical conditions where heat accumulates. In contrast, we propose the concept of equivalent infinite cooling time interval, based on which the real-spot (RS) melting strategy can significantly reduce macroscopic residual stresses. The underlying mechanisms are elucidated by revealing the dual effect of heat accumulation on residual stresses and strains, which induces a trade-off between their peak levels and total affected areas. Moreover, we demonstrate that the RS melting strategy alleviates continuous compressive plastic deformation in melt region and HAZ by reshaping principal plastic strain orientations and alternating compressive and tensile plastic strain components. This enables reducing residual stresses while increasing cumulative plastic strains, thereby overcoming the limitations in mechanical field control imposed by the positive correlation between residual stresses and strains.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"31 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2026-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147447153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-14DOI: 10.1016/j.actamat.2026.122120
Luciano Borasi, Steven E. Kooi, Christopher A. Schuh
{"title":"Crossing from thermally activated to drag-controlled plasticity in mild steel as strain rate increases","authors":"Luciano Borasi, Steven E. Kooi, Christopher A. Schuh","doi":"10.1016/j.actamat.2026.122120","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122120","url":null,"abstract":"","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"16 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2026-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147448377","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-14DOI: 10.1016/j.actamat.2026.122121
Haoliang Xiang, Yue Wu, Dean Liu, Bin Li, Xiaofen Li, Wei Wu, Yue Zhao
The introduction of a transient liquid phase into industrial pulsed laser deposition (PLD) systems has enabled the ultrahigh-rate growth of superconducting films (≥ 100 nm s−1), allowing opportunities for cost-effective, large-scale fabrication of second-generation high-temperature superconducting tapes. However, the growth mechanism of superconducting films under ultrahigh-rate industrial PLD conditions remains unclear. Here, a statistical investigation of industrial samples is conducted and a plate-like orthorhombic BaCu3O4 phase is identified for the first time on the EuBa2Cu3O7−δ (EuBCO) surface, which shows strong correlation with its superconducting performance. Comprehensive characterization reveals that BaCu3O4 is an epitaxially stabilized intermediate phase. Notably, BaCu3O4 plays a key role in the high-rate epitaxial growth of EuBCO by reacting with the Y/Eu species that migrate to the growth front, forming superconducting phases — a mechanism further supported by the formation of oriented YBa2Cu3O7−δ. Based on these results, a growth model is proposed whereby the epitaxial BaCu3O4 intermediate phase serves as a crucial reactant, driving the formation of c-axis-oriented EuBCO in transient liquid-assisted growth. This work provides novel insights into the underlying mechanisms of transient liquid-assisted growth in PLD-grown REBa2Cu3O7−δ films and establishes a framework for further optimization of industrial PLD processes.
在工业脉冲激光沉积（PLD）系统中引入瞬态液相，使得超导薄膜（≥100 nm s - 1）的超高速率生长成为可能，从而为第二代高温超导带的大规模制造提供了经济高效的机会。然而，超高速工业PLD条件下超导薄膜的生长机制尚不清楚。本文通过对工业样品的统计研究，首次在EuBa2Cu3O7−δ (EuBCO)表面发现了一种类似板状的正交相，该相与其超导性能有很强的相关性。综合表征表明BaCu3O4是外延稳定的中间相。值得注意的是，BaCu3O4通过与迁移到生长前沿的Y/Eu物质反应形成超导相，在EuBCO的高速率外延生长中发挥了关键作用，这一机制得到了YBa2Cu3O7−δ取向形成的进一步支持。基于这些结果，提出了一种生长模型，其中外延BaCu3O4中间相作为关键的反应物，在瞬态液体辅助生长中驱动c轴取向EuBCO的形成。这项工作为PLD生长的REBa2Cu3O7−δ薄膜的瞬态液体辅助生长的潜在机制提供了新的见解，并为进一步优化工业PLD工艺建立了框架。
{"title":"Observation and Role of Epitaxial BaCu3O4 Phase in Ultrahigh-Rate EuBa2Cu3O7−δ Film Growth via Industrial Pulsed Laser Deposition","authors":"Haoliang Xiang, Yue Wu, Dean Liu, Bin Li, Xiaofen Li, Wei Wu, Yue Zhao","doi":"10.1016/j.actamat.2026.122121","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122121","url":null,"abstract":"The introduction of a transient liquid phase into industrial pulsed laser deposition (PLD) systems has enabled the ultrahigh-rate growth of superconducting films (≥ 100 nm s<sup>−1</sup>), allowing opportunities for cost-effective, large-scale fabrication of second-generation high-temperature superconducting tapes. However, the growth mechanism of superconducting films under ultrahigh-rate industrial PLD conditions remains unclear. Here, a statistical investigation of industrial samples is conducted and a plate-like orthorhombic BaCu<sub>3</sub>O<sub>4</sub> phase is identified for the first time on the EuBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−</sub><em><sub>δ</sub></em> (EuBCO) surface, which shows strong correlation with its superconducting performance. Comprehensive characterization reveals that BaCu<sub>3</sub>O<sub>4</sub> is an epitaxially stabilized intermediate phase. Notably, BaCu<sub>3</sub>O<sub>4</sub> plays a key role in the high-rate epitaxial growth of EuBCO by reacting with the Y/Eu species that migrate to the growth front, forming superconducting phases — a mechanism further supported by the formation of oriented YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−</sub><em><sub>δ</sub></em>. Based on these results, a growth model is proposed whereby the epitaxial BaCu<sub>3</sub>O<sub>4</sub> intermediate phase serves as a crucial reactant, driving the formation of <em>c</em>-axis-oriented EuBCO in transient liquid-assisted growth. This work provides novel insights into the underlying mechanisms of transient liquid-assisted growth in PLD-grown REBa<sub>2</sub>Cu<sub>3</sub>O<sub>7−</sub><em><sub>δ</sub></em> films and establishes a framework for further optimization of industrial PLD processes.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"44 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2026-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147447476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-14DOI: 10.1016/j.actamat.2026.122126
Soumya Bandyopadhyay, Sourav Chatterjee, Dallas R. Trinkle, Richard G. Hennig, Victoria Miller, Michael S. Kesler, Michael R. Tonks
Applied magnetic fields can alter phase equilibria and kinetics in steels; however, quantitatively resolving how magnetic, chemical, and elastic driving forces jointly influence the microstructure remains challenging. We develop a quantitative magneto-mechanically coupled phase-field model for the Fe-C system that couples a CALPHAD-based chemical free energy with demagnetization-field magnetostatics and microelasticity. The model reproduces single- and multi-particle evolution during the inverse transformation at 1023 K under external fields up to 20 T, including ellipsoidal morphologies observed experimentally at 8 T. Chemically driven growth is isotropic; a magnetic interaction introduces an anisotropic driving force that elongates precipitates along the field into ellipsoids, while elastic coherency promotes faceting, yielding elongated cuboidal or “brick-like” particles under combined magneto-elastic coupling. Growth kinetics increase with C content, and decrease with field strength and misfit strain. Multi-particle simulations reveal dipolar interaction-mediated coalescence for field-parallel neighbors and ripening for field-perpendicular neighbors. Incorporating field-dependent diffusivity from experiment slows kinetics as expected; a first-principles-motivated anisotropic diffusivity correction is estimated to be small (2%). These results establish a process-structure link for magnetically assisted heat treatments of Fe-C alloys and provide guidance for microstructure control via chemo-magneto-mechanical synergism.
{"title":"Effect of magneto-mechanical synergism in the process-structure correlation in Fe-C alloys: A phase-field modeling approach","authors":"Soumya Bandyopadhyay, Sourav Chatterjee, Dallas R. Trinkle, Richard G. Hennig, Victoria Miller, Michael S. Kesler, Michael R. Tonks","doi":"10.1016/j.actamat.2026.122126","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122126","url":null,"abstract":"Applied magnetic fields can alter phase equilibria and kinetics in steels; however, quantitatively resolving how magnetic, chemical, and elastic driving forces jointly influence the microstructure remains challenging. We develop a quantitative magneto-mechanically coupled phase-field model for the Fe-C system that couples a CALPHAD-based chemical free energy with demagnetization-field magnetostatics and microelasticity. The model reproduces single- and multi-particle evolution during the <span><math><mrow is=\"true\"><mi is=\"true\">α</mi><mo is=\"true\">→</mo><mi is=\"true\">γ</mi></mrow></math></span> inverse transformation at 1023 K under external fields up to 20 T, including ellipsoidal morphologies observed experimentally at 8 T. Chemically driven growth is isotropic; a magnetic interaction introduces an anisotropic driving force that elongates <span><math><mi is=\"true\">γ</mi></math></span> precipitates along the field into ellipsoids, while elastic coherency promotes faceting, yielding elongated cuboidal or “brick-like” particles under combined magneto-elastic coupling. Growth kinetics increase with C content, and decrease with field strength and misfit strain. Multi-particle simulations reveal dipolar interaction-mediated coalescence for field-parallel neighbors and ripening for field-perpendicular neighbors. Incorporating field-dependent diffusivity from experiment slows kinetics as expected; a first-principles-motivated anisotropic diffusivity correction is estimated to be small (<span><math><mo is=\"true\"><</mo></math></span>2%). These results establish a process-structure link for magnetically assisted heat treatments of Fe-C alloys and provide guidance for microstructure control via chemo-magneto-mechanical synergism.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"34 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2026-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147447167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-13DOI: 10.1016/j.actamat.2026.122109
Thomas P. Matson, Nutth Tuchinda, Christopher A. Schuh
Grain boundaries are comprised of a wide variety of different atomic sites, and each of those sites has its own local environment, energetics, and tendency to attract or repel the solute elements dissolved in an alloy. The chemical segregation of solutes to grain boundaries is a classical and pervasive problem in materials science, but treatment of the full spectrum of grain boundary sites in a generalized polycrystalline ensemble has not been rigorously possible until recently. This overview article holistically summarizes the recent rapid developments in such spectral modeling, and foreshadows those coming in the future. Beginning from self-consistent definitions of the thermodynamic site properties (enthalpy and excess entropy of segregation), considering the solute interactions at non-dilute concentrations, and treating the statistical mechanics of configurational entropy, we elaborate the use of a full, multi-variate segregation isotherm that can be applied to any binary alloy system. We review the existing computational methods of determining those spectra, and survey spectral databases developed for thousands of alloys at various levels of accuracy. Preferred sets of spectral parameters are provided for appropriately simplified versions of the segregation isotherm, to facilitate wide usage of the model. We proceed to highlight the key successes of the spectral model, including its validation against full atomistic Monte Carlo simulations and a variety of experiments. Alloy design efforts that use spectral data to target interesting segregation behaviors are illustrated, including extensions to complex cases like ternary alloys with solutes that collaborate to fill grain boundary sites, and nanocrystalline alloys with stable grain boundaries. The state of the spectral model is sufficiently robust that significant physical problems with historical, non-spectral models are now coming more clearly to light; the time is right for broader replacement of historical models with spectral ones.
{"title":"Overview: The Spectral Model of Grain Boundary Segregation","authors":"Thomas P. Matson, Nutth Tuchinda, Christopher A. Schuh","doi":"10.1016/j.actamat.2026.122109","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122109","url":null,"abstract":"Grain boundaries are comprised of a wide variety of different atomic sites, and each of those sites has its own local environment, energetics, and tendency to attract or repel the solute elements dissolved in an alloy. The chemical segregation of solutes to grain boundaries is a classical and pervasive problem in materials science, but treatment of the full spectrum of grain boundary sites in a generalized polycrystalline ensemble has not been rigorously possible until recently. This overview article holistically summarizes the recent rapid developments in such spectral modeling, and foreshadows those coming in the future. Beginning from self-consistent definitions of the thermodynamic site properties (enthalpy and excess entropy of segregation), considering the solute interactions at non-dilute concentrations, and treating the statistical mechanics of configurational entropy, we elaborate the use of a full, multi-variate segregation isotherm that can be applied to any binary alloy system. We review the existing computational methods of determining those spectra, and survey spectral databases developed for thousands of alloys at various levels of accuracy. Preferred sets of spectral parameters are provided for appropriately simplified versions of the segregation isotherm, to facilitate wide usage of the model. We proceed to highlight the key successes of the spectral model, including its validation against full atomistic Monte Carlo simulations and a variety of experiments. Alloy design efforts that use spectral data to target interesting segregation behaviors are illustrated, including extensions to complex cases like ternary alloys with solutes that collaborate to fill grain boundary sites, and nanocrystalline alloys with stable grain boundaries. The state of the spectral model is sufficiently robust that significant physical problems with historical, non-spectral models are now coming more clearly to light; the time is right for broader replacement of historical models with spectral ones.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"45 1","pages":""},"PeriodicalIF":9.4,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147447151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-13DOI: 10.1016/j.actamat.2026.122108
Esther C. Hessong, Zhengyu Zhang, Tianjiao Lei, Mingjie Xu, Toshihiro Aoki, Timothy J. Rupert
Amorphous interfacial complexions have been shown to restrict grain growth and improve damage tolerance in nanocrystalline alloys, with increased chemical complexity stabilizing the complexions themselves. Here, we investigate local chemical composition and structural short-range order in Cu-rich, multi-component nanocrystalline alloys to understand how dopants self-organize within these amorphous complexions and how local structure is altered. High resolution scanning transmission electron microscopy and elemental analysis are used to study both grain boundaries and interphase boundaries, with chemical partitioning observed for both. Notably, the amorphous-crystalline transition region is observed to be enriched in certain dopant species and depleted of others as compared to the interior of the amorphous complexions. This chemical patterning can be explained in terms of the elemental preference for ordered or disordered grain boundary environments. As only a qualitative measure of structural short-range order can be obtained with nanobeam electron diffraction for these specimens, atomistic simulations with a custom-built machine learning interatomic potential are then used to probe how dopant patterning affects local structural state. Increased grain boundary chemical complexity is found to result in a more disordered complexion structure, with segregation to the amorphous-crystalline transition regions driving changes in local structure that are sensitive to dopant ratios. As a whole, the intimate connection between local chemistry and order in amorphous interfacial complexions is demonstrated, opening the door for microstructural engineering within the amorphous complexions themselves.
{"title":"Modulation of structural short-range order due to chemical patterning in multi-component amorphous interfacial complexions","authors":"Esther C. Hessong, Zhengyu Zhang, Tianjiao Lei, Mingjie Xu, Toshihiro Aoki, Timothy J. Rupert","doi":"10.1016/j.actamat.2026.122108","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122108","url":null,"abstract":"Amorphous interfacial complexions have been shown to restrict grain growth and improve damage tolerance in nanocrystalline alloys, with increased chemical complexity stabilizing the complexions themselves. Here, we investigate local chemical composition and structural short-range order in Cu-rich, multi-component nanocrystalline alloys to understand how dopants self-organize within these amorphous complexions and how local structure is altered. High resolution scanning transmission electron microscopy and elemental analysis are used to study both grain boundaries and interphase boundaries, with chemical partitioning observed for both. Notably, the amorphous-crystalline transition region is observed to be enriched in certain dopant species and depleted of others as compared to the interior of the amorphous complexions. This chemical patterning can be explained in terms of the elemental preference for ordered or disordered grain boundary environments. As only a qualitative measure of structural short-range order can be obtained with nanobeam electron diffraction for these specimens, atomistic simulations with a custom-built machine learning interatomic potential are then used to probe how dopant patterning affects local structural state. Increased grain boundary chemical complexity is found to result in a more disordered complexion structure, with segregation to the amorphous-crystalline transition regions driving changes in local structure that are sensitive to dopant ratios. As a whole, the intimate connection between local chemistry and order in amorphous interfacial complexions is demonstrated, opening the door for microstructural engineering within the amorphous complexions themselves.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"54 1","pages":"122108"},"PeriodicalIF":9.4,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147461806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-03-13DOI: 10.1016/j.actamat.2026.122104
Jin Zhang, Bo-Yu Liu, Kun Luo, Yao-Feng Li, Huan-Huan Lu, Fei Liu, Bin Li, Upadrasta Ramamurty, Qi An, Zhi-Wei Shan
Electroplasticity, enhancement of plasticity in metals by electric current, has been widely reported for decades, yet a clear mechanistic understanding of its origins has remained elusive. While Joule heating could play a role, it has long been hypothesized that electroplasticity may originate from athermal current-defect interactions. However, quantitative experimental validation regarding the athermal effect remains scarce and challenging. In this work, we conduct in-situ electro-mechanical testing under short electrical pulses, and achieve real-time, quantitative tracking of the motion of individual hard-to-glide pyramidal dislocations, which are known for their high critical stresses and low mobility in magnesium under conventional conditions. Under short current pulses that induce negligible temperature rise, we detect a pronounced reduction in flow stress and a significant decrease in the critical stress for pyramidal dislocation glide. Real-time, single-dislocation tracking reveals a current-induced transition from intermittent, jerky motion to smooth and continuous glide, evidencing a marked enhancement in dislocation mobility. First-principles calculations demonstrate that electron injection weakens atomic bonding at the dislocation core, reducing the energy barrier for glide. Our findings establish an athermal mechanism for electroplasticity: electric current facilitates the motion of hard-to-glide dislocations through bond softening at the core.
{"title":"Bond Weakening at the Dislocation Core: An Athermal Mechanism for Current-Induced Plasticity in Magnesium","authors":"Jin Zhang, Bo-Yu Liu, Kun Luo, Yao-Feng Li, Huan-Huan Lu, Fei Liu, Bin Li, Upadrasta Ramamurty, Qi An, Zhi-Wei Shan","doi":"10.1016/j.actamat.2026.122104","DOIUrl":"https://doi.org/10.1016/j.actamat.2026.122104","url":null,"abstract":"Electroplasticity, enhancement of plasticity in metals by electric current, has been widely reported for decades, yet a clear mechanistic understanding of its origins has remained elusive. While Joule heating could play a role, it has long been hypothesized that electroplasticity may originate from athermal current-defect interactions. However, quantitative experimental validation regarding the athermal effect remains scarce and challenging. In this work, we conduct <em>in-situ</em> electro-mechanical testing under short electrical pulses, and achieve real-time, quantitative tracking of the motion of individual hard-to-glide pyramidal dislocations, which are known for their high critical stresses and low mobility in magnesium under conventional conditions. Under short current pulses that induce negligible temperature rise, we detect a pronounced reduction in flow stress and a significant decrease in the critical stress for pyramidal dislocation glide. Real-time, single-dislocation tracking reveals a current-induced transition from intermittent, jerky motion to smooth and continuous glide, evidencing a marked enhancement in dislocation mobility. First-principles calculations demonstrate that electron injection weakens atomic bonding at the dislocation core, reducing the energy barrier for glide. Our findings establish an athermal mechanism for electroplasticity: electric current facilitates the motion of hard-to-glide dislocations through bond softening at the core.","PeriodicalId":238,"journal":{"name":"Acta Materialia","volume":"146 1","pages":"122104"},"PeriodicalIF":9.4,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147461805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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