Imparting a gradient microstructure combined with residual compressive stress in the surface layer is an attractive strategy for enhancing the fatigue resistance of alloys. However, a counterintuitive reduction in the fatigue strength (σ−1) in such alloys is often reported, and its underlying mechanism remains unclear. In this study, the Inconel 718 nickel-based alloy was subjected to an ultrasonic surface rolling process, and the effects of microstructural, residual stress, and hardness gradients on the fully reversed tension-compression σ−1 are studied. Experimental results show a peak in the data of σ−1 versus normalized fatigue crack initiation radius ratio (A), a normalized parameter that captures geometric effects on crack initiation sites and is associated with stress state (stress triaxiality (Tr)). Detailed analysis and microstructural characterization show that the observed peak is a result of the competition between the Tr—governed dislocation driving force (τd) and the microstructure-dictated resistance (τc) at fatigue small crack tip, which was substantiated by recourse to molecular dynamics simulations. Based on these findings, a fracture mechanics-based model that considers the residual stress fields, A, Tr, τd, and τc for predicting the σ−1 variations is developed and validated. This work establishes a theoretical framework and design methodology for enhancing the σ−1 of structural components subjected to cyclic loads through surface modification.
{"title":"Toward peak fatigue strength in surface-strengthened gradient Inconel 718 alloy via balancing stress-triaxiality-governed dislocation driving force and microstructure-dictated resistance","authors":"Xinmao Qin, Yilong Liang, Peng Chen, Fei Li, Xu Huang, Jianhua Deng, Lingling Wang, Guigui Peng, Tianle Li, Xiaochun Liu, Wanjun Yan, Liqiong Zhong, Fei Liu, Upadrasta Ramamurty","doi":"10.1016/j.jmst.2025.12.017","DOIUrl":"https://doi.org/10.1016/j.jmst.2025.12.017","url":null,"abstract":"Imparting a gradient microstructure combined with residual compressive stress in the surface layer is an attractive strategy for enhancing the fatigue resistance of alloys. However, a counterintuitive reduction in the fatigue strength (<ce:italic>σ</ce:italic><ce:inf loc=\"post\">−1</ce:inf>) in such alloys is often reported, and its underlying mechanism remains unclear. In this study, the Inconel 718 nickel-based alloy was subjected to an ultrasonic surface rolling process, and the effects of microstructural, residual stress, and hardness gradients on the fully reversed tension-compression <ce:italic>σ</ce:italic><ce:inf loc=\"post\">−1</ce:inf> are studied. Experimental results show a peak in the data of <ce:italic>σ</ce:italic><ce:inf loc=\"post\">−1</ce:inf> versus normalized fatigue crack initiation radius ratio (<ce:italic>A</ce:italic>), a normalized parameter that captures geometric effects on crack initiation sites and is associated with stress state (stress triaxiality (Tr)). Detailed analysis and microstructural characterization show that the observed peak is a result of the competition between the Tr—governed dislocation driving force (<mml:math altimg=\"si15.svg\"><mml:msub><mml:mi>τ</mml:mi><mml:mi mathvariant=\"normal\">d</mml:mi></mml:msub></mml:math>) and the microstructure-dictated resistance (<mml:math altimg=\"si16.svg\"><mml:msub><mml:mi>τ</mml:mi><mml:mi mathvariant=\"normal\">c</mml:mi></mml:msub></mml:math>) at fatigue small crack tip, which was substantiated by recourse to molecular dynamics simulations. Based on these findings, a fracture mechanics-based model that considers the residual stress fields, <ce:italic>A</ce:italic>, Tr, <mml:math altimg=\"si15.svg\"><mml:msub><mml:mi>τ</mml:mi><mml:mi mathvariant=\"normal\">d</mml:mi></mml:msub></mml:math>, and <mml:math altimg=\"si16.svg\"><mml:msub><mml:mi>τ</mml:mi><mml:mi mathvariant=\"normal\">c</mml:mi></mml:msub></mml:math> for predicting the <ce:italic>σ</ce:italic><ce:inf loc=\"post\">−1</ce:inf> variations is developed and validated. This work establishes a theoretical framework and design methodology for enhancing the <ce:italic>σ</ce:italic><ce:inf loc=\"post\">−1</ce:inf> of structural components subjected to cyclic loads through surface modification.","PeriodicalId":16154,"journal":{"name":"Journal of Materials Science & Technology","volume":"1 1","pages":""},"PeriodicalIF":10.9,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145760377","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 : 2025-12-13DOI: 10.1016/j.jmst.2025.12.016
Xiaoying Qian, Zhihua Dong, Bin Jiang, Zhiying Zheng, Ang Zhang, Changle Li, Levente Vitos
The underlying mechanism of co-segregation of alloying elements at the grain boundary and its influence on mechanical properties are elaborated in Mg-Zn-Ca alloys by integrated experimental characterizations and ab initio calculations. Significant co-segregation of Zn and Ca at the grain boundary is detected in the Mg-Zn-Ca ternary alloy, leading to an important contribution to the simultaneous improvement of strength and ductility. The relatively strong electronic interactions between Zn and Ca are demonstrated to promote the formation of Zn-Ca ionic bonds and greatly decrease the segregation energy. It, in combination with the atomic-size-related preferred occupations of Zn and Ca, primarily contributes to their significant co-segregation at the grain boundary. The obvious co-segregation of Zn and Ca remarkably decreases grain size, significantly contributing to the improved strength. In addition, coarse twins and the associated cracking are efficiently suppressed in plastic deformation owing to the decreased grain size. Furthermore, the co-segregation significantly increases grain boundary cohesion strength and decreases grain boundary energy, which can delay the initiation of grain boundary cracks and accommodate high stress to activate non-basal slips. In addition, the high-angle grain boundaries stabilized by alloying element co-segregation promote the transmission of non-basal slip pairs and stress relaxation at the grain boundary and improve ductility ultimately. The present advances enhance the understanding required for evading the strength and ductility trade-off in Mg alloys by tailoring alloying element segregation.
{"title":"Mechanism of alloying element co-segregation at the grain boundary and its influence on mechanical properties in Mg-Zn-Ca alloy","authors":"Xiaoying Qian, Zhihua Dong, Bin Jiang, Zhiying Zheng, Ang Zhang, Changle Li, Levente Vitos","doi":"10.1016/j.jmst.2025.12.016","DOIUrl":"https://doi.org/10.1016/j.jmst.2025.12.016","url":null,"abstract":"The underlying mechanism of co-segregation of alloying elements at the grain boundary and its influence on mechanical properties are elaborated in Mg-Zn-Ca alloys by integrated experimental characterizations and <em>ab initio</em> calculations. Significant co-segregation of Zn and Ca at the grain boundary is detected in the Mg-Zn-Ca ternary alloy, leading to an important contribution to the simultaneous improvement of strength and ductility. The relatively strong electronic interactions between Zn and Ca are demonstrated to promote the formation of Zn-Ca ionic bonds and greatly decrease the segregation energy. It, in combination with the atomic-size-related preferred occupations of Zn and Ca, primarily contributes to their significant co-segregation at the grain boundary. The obvious co-segregation of Zn and Ca remarkably decreases grain size, significantly contributing to the improved strength. In addition, coarse twins and the associated cracking are efficiently suppressed in plastic deformation owing to the decreased grain size. Furthermore, the co-segregation significantly increases grain boundary cohesion strength and decreases grain boundary energy, which can delay the initiation of grain boundary cracks and accommodate high stress to activate non-basal slips. In addition, the high-angle grain boundaries stabilized by alloying element co-segregation promote the transmission of non-basal slip pairs and stress relaxation at the grain boundary and improve ductility ultimately. The present advances enhance the understanding required for evading the strength and ductility trade-off in Mg alloys by tailoring alloying element segregation.","PeriodicalId":16154,"journal":{"name":"Journal of Materials Science & Technology","volume":"148 1","pages":""},"PeriodicalIF":10.9,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145732200","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}
β-FeOOH, a key corrosion product formed in coastal atmospheric environments, plays a pivotal role in governing the corrosion kinetics of steel through its electrochemical reduction. However, the detailed electrochemical reduction pathways in environments containing both H+ and Cl− ions remain insufficiently understood. Here, first-principles calculations both validate existing models and uncover previously unrecognized interactions in the cathodic reduction of β-FeOOH. The calculations reveal distinct bonding modes: H+ ions form covalent bonds with tunnel wall oxygen atoms, while Cl− ions occupy tunnel centers and interact ionically with wall hydrogen atoms. The incorporation of [H+/Cl−] ion pairs markedly enhances electrochemical stability and electron affinity, with β-FeOOH(H+, Cl−)0.167 showing maximum stabilization. Ion-migration analysis shows that Cl− exhibits lower migration barriers than H+, leading to preferential Cl− desorption under humid conditions. This forms localized β-FeOOH(H+) oxonium intermediates, which were previously unanticipated. Upon electron uptake, these oxonium species reduce Fe(III) to Fe(II), causing FeO6 expansion and initiating dehydration reactions. Ultimately, phase transformation to Fe3O4 is achieved through the reorganization of the local coordination environment. These results provide mechanistic insights into the electrochemical reduction of β-FeOOH and reveal previously unanticipated electrochemical steps, offering guidance for predicting steel corrosion in marine environments and developing effective protection strategies.
{"title":"First-principles investigation of H+/Cl−-mediated electrochemical reduction of β-FeOOH under coastal atmospheric conditions","authors":"Chen Liu, Chao Li, Jie Wei, Xin Wei, Changgang Wang, Junhua Dong, Xing-Qiu Chen","doi":"10.1016/j.jmst.2025.11.056","DOIUrl":"https://doi.org/10.1016/j.jmst.2025.11.056","url":null,"abstract":"β-FeOOH, a key corrosion product formed in coastal atmospheric environments, plays a pivotal role in governing the corrosion kinetics of steel through its electrochemical reduction. However, the detailed electrochemical reduction pathways in environments containing both H<sup>+</sup> and Cl<sup>−</sup> ions remain insufficiently understood. Here, first-principles calculations both validate existing models and uncover previously unrecognized interactions in the cathodic reduction of β-FeOOH. The calculations reveal distinct bonding modes: H<sup>+</sup> ions form covalent bonds with tunnel wall oxygen atoms, while Cl<sup>−</sup> ions occupy tunnel centers and interact ionically with wall hydrogen atoms. The incorporation of [H<sup>+</sup>/Cl<sup>−</sup>] ion pairs markedly enhances electrochemical stability and electron affinity, with β-FeOOH(H<sup>+</sup>, Cl<sup>−</sup>)<sub>0.167</sub> showing maximum stabilization. Ion-migration analysis shows that Cl<sup>−</sup> exhibits lower migration barriers than H<sup>+</sup>, leading to preferential Cl<sup>−</sup> desorption under humid conditions. This forms localized β-FeOOH(H<sup>+</sup>) oxonium intermediates, which were previously unanticipated. Upon electron uptake, these oxonium species reduce Fe(III) to Fe(II), causing FeO<sub>6</sub> expansion and initiating dehydration reactions. Ultimately, phase transformation to Fe<sub>3</sub>O<sub>4</sub> is achieved through the reorganization of the local coordination environment. These results provide mechanistic insights into the electrochemical reduction of β-FeOOH and reveal previously unanticipated electrochemical steps, offering guidance for predicting steel corrosion in marine environments and developing effective protection strategies.","PeriodicalId":16154,"journal":{"name":"Journal of Materials Science & Technology","volume":"9 1","pages":""},"PeriodicalIF":10.9,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145728931","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 : 2025-12-12DOI: 10.1016/j.jmst.2025.12.015
Xinyuan Wang, Cédric Bourgès, Longquan Wang, Gang Wu, Xinzhi Wu, Takao Mori
Synergizing high performance and long-term stability in thermoelectric materials remains a formidable challenge, particularly for eco-friendly Cu–S compounds, which have outstanding performance but are plagued by thermal degradation at elevated temperatures and copper ion migration under electric fields. Herein, a promising in-situ heterostructure (Cu2−xS–CuInS2) strategy induced by iso-atomic In substitution in Cu1.93S was demonstrated to unlock the threefold balance among thermoelectric performance, thermal stability, and electrical stability. This strategy tunes the Cu vacancy content in the primary Cu2−xS phase and the fraction of the secondary CuInS2 phase, thereby suppressing carrier scattering while preserving ultralow lattice thermal conductivity and a high power factor. The optimized Cu1.89In0.04S achieves a peak zT of 1.57 at 873 K and an average zT of 1.31 over 723–873 K, ranking among the highest values within binary Cu–S thermoelectrics. Crucially, the heterostructure strategy imparts exceptional durability, as evidenced by negligible degradation under thermal cycling and remarkable resistance to current-induced failure, wherein ionic hysteresis at heterointerfaces suppresses Cu migration. Overall, these results underscore heterostructure engineering as a compelling route to transcend the intrinsic limitations of Cu–S compounds, charting a pathway toward next-generation of thermoelectric materials that couple high performance with long-term reliability.
{"title":"Constructing in-situ heterostructure toward high-performance and stable Cu–S thermoelectrics","authors":"Xinyuan Wang, Cédric Bourgès, Longquan Wang, Gang Wu, Xinzhi Wu, Takao Mori","doi":"10.1016/j.jmst.2025.12.015","DOIUrl":"https://doi.org/10.1016/j.jmst.2025.12.015","url":null,"abstract":"Synergizing high performance and long-term stability in thermoelectric materials remains a formidable challenge, particularly for eco-friendly Cu–S compounds, which have outstanding performance but are plagued by thermal degradation at elevated temperatures and copper ion migration under electric fields. Herein, a promising in-situ heterostructure (Cu<sub>2−</sub><em><sub>x</sub></em>S–CuInS<sub>2</sub>) strategy induced by iso-atomic In substitution in Cu<sub>1.93</sub>S was demonstrated to unlock the threefold balance among thermoelectric performance, thermal stability, and electrical stability. This strategy tunes the Cu vacancy content in the primary Cu<sub>2−</sub><em><sub>x</sub></em>S phase and the fraction of the secondary CuInS<sub>2</sub> phase, thereby suppressing carrier scattering while preserving ultralow lattice thermal conductivity and a high power factor. The optimized Cu<sub>1.89</sub>In<sub>0.04</sub>S achieves a peak <em>zT</em> of 1.57 at 873 K and an average <em>zT</em> of 1.31 over 723–873 K, ranking among the highest values within binary Cu–S thermoelectrics. Crucially, the heterostructure strategy imparts exceptional durability, as evidenced by negligible degradation under thermal cycling and remarkable resistance to current-induced failure, wherein ionic hysteresis at heterointerfaces suppresses Cu migration. Overall, these results underscore heterostructure engineering as a compelling route to transcend the intrinsic limitations of Cu–S compounds, charting a pathway toward next-generation of thermoelectric materials that couple high performance with long-term reliability.","PeriodicalId":16154,"journal":{"name":"Journal of Materials Science & Technology","volume":"8 1","pages":""},"PeriodicalIF":10.9,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145728934","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 : 2025-12-11DOI: 10.1016/j.jmst.2025.12.012
Chun Du, Jiayun Su, Ziyang Liu, Zhaoqiang Zheng, Jiandong Yao, Yicun Chen, Xuanming Duan
Two-dimensional (2D) van der Waals heterostructures offer a promising platform for advanced optoelectronics. However, conventional type-II configurations with Fermi level offsets unavoidably introduce band bending and trap-assisted recombination, restricting photoelectric conversion efficiency. Here, a size-effect-controlled strategy is employed to intrinsically align Fermi levels across the MoS2/ReS2 interface while preserving type-II band alignment. The resulting heterojunction exhibits nearly zero Fermi level offset, thereby eliminating interfacial barriers and prolonging carrier lifetime. Under low-power ultraviolet excitation, the device delivers a responsivity of 4.53 × 104 A/W, an external quantum efficiency of 1.5 × 107%, and a specific detectivity of 1.6 × 1014 Jones. Spectroscopic and ultrafast carrier dynamics analyses demonstrate that the precise Fermi level plays a more decisive role in governing charge separation than conventional built-in fields. Comparative investigations further confirm that increasing the Fermi level mismatch induces pronounced band bending, trap-assisted recombination, and substantial photoresponse degradation. In contrast, optimized alignment maximizes charge transfer efficiency, as evidenced by 77.3% photoluminescence quenching. Additionally, the optimized heterostructure supports broadband detection and enables high-resolution imaging, demonstrating strong application potential. This work establishes interfacial electronic equilibrium as a pivotal design principle and introduces a general, doping-free framework for Fermi level regulation in 2D heterostructures, offering mechanistic insights and scalable guidance for next-generation optoelectronic and imaging devices.
二维（2D）范德华异质结构为先进光电子学提供了一个有前途的平台。然而，具有费米能级偏移的传统ii型结构不可避免地引入了能带弯曲和阱辅助复合，限制了光电转换效率。在这里，采用尺寸效应控制策略来在MoS2/ReS2界面上本质对齐费米能级，同时保持ii型波段对准。所得到的异质结显示出几乎为零的费米能级偏移，从而消除了界面障碍并延长了载流子寿命。在低功率紫外激发下，该器件的响应率为4.53 × 104 a /W，外量子效率为1.5 × 107%，比探测率为1.6 × 1014 Jones。光谱和超快载流子动力学分析表明，精确的费米能级在控制电荷分离方面比传统的内置场起着更决定性的作用。比较研究进一步证实，增加费米能级失配会导致明显的能带弯曲、阱辅助重组和明显的光响应退化。相反，优化后的排列使电荷转移效率最大化，光致发光猝灭率达到77.3%。此外，优化后的异质结构支持宽带检测并实现高分辨率成像，显示出强大的应用潜力。这项工作建立了界面电子平衡作为一个关键的设计原则，并为二维异质结构中的费米能级调节引入了一个通用的、无掺杂的框架，为下一代光电和成像器件提供了机制见解和可扩展的指导。
{"title":"Nearly zero Fermi level offset in MoS2/ReS2 heterojunctions for enhanced photoresponse","authors":"Chun Du, Jiayun Su, Ziyang Liu, Zhaoqiang Zheng, Jiandong Yao, Yicun Chen, Xuanming Duan","doi":"10.1016/j.jmst.2025.12.012","DOIUrl":"https://doi.org/10.1016/j.jmst.2025.12.012","url":null,"abstract":"Two-dimensional (2D) van der Waals heterostructures offer a promising platform for advanced optoelectronics. However, conventional type-II configurations with Fermi level offsets unavoidably introduce band bending and trap-assisted recombination, restricting photoelectric conversion efficiency. Here, a size-effect-controlled strategy is employed to intrinsically align Fermi levels across the MoS<sub>2</sub>/ReS<sub>2</sub> interface while preserving type-II band alignment. The resulting heterojunction exhibits nearly zero Fermi level offset, thereby eliminating interfacial barriers and prolonging carrier lifetime. Under low-power ultraviolet excitation, the device delivers a responsivity of 4.53 × 10<sup>4</sup> A/W, an external quantum efficiency of 1.5 × 10<sup>7</sup>%, and a specific detectivity of 1.6 × 10<sup>14</sup> Jones. Spectroscopic and ultrafast carrier dynamics analyses demonstrate that the precise Fermi level plays a more decisive role in governing charge separation than conventional built-in fields. Comparative investigations further confirm that increasing the Fermi level mismatch induces pronounced band bending, trap-assisted recombination, and substantial photoresponse degradation. In contrast, optimized alignment maximizes charge transfer efficiency, as evidenced by 77.3% photoluminescence quenching. Additionally, the optimized heterostructure supports broadband detection and enables high-resolution imaging, demonstrating strong application potential. This work establishes interfacial electronic equilibrium as a pivotal design principle and introduces a general, doping-free framework for Fermi level regulation in 2D heterostructures, offering mechanistic insights and scalable guidance for next-generation optoelectronic and imaging devices.","PeriodicalId":16154,"journal":{"name":"Journal of Materials Science & Technology","volume":"29 1","pages":""},"PeriodicalIF":10.9,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145732201","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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