Pub Date : 2026-01-02DOI: 10.1016/j.ijplas.2025.104605
Tolga Berkay Celebi , Orcun Koray Celebi , Daegun You , Ahmed Sameer Khan Mohammed , Ashley Bucsek , Huseyin Sehitoglu
This study investigates the mechanics of prismatic and first-order pyramidal slip in titanium (Ti), elucidating the physics of easy-glide and cross-slip through a combination of theory and experiments. Screw-character prismatic (Pr) dislocations in Ti are of particular interest because their complex cores can be stable or unstable, leading to activation by either cross-slip or planar glide. To investigate these mechanisms, site-specific micro tensile samples were prepared using focused ion beam (FIB) milling and mounted on a push-to-pull (PTP) device for in-situ transmission electron microscopy (TEM) tensile testing. The in-situ experiments provide direct observations of the onset of dislocation motion and the precise determination of the critical resolved shear stress (CRSS) for the activated mechanisms, and its evolution with load cycling. A comprehensive theory has been developed to predict the CRSS values for easy glide, cross-slip, and multiplication of dislocations. Predicted critical stresses for pyramidal (π)-to-Pr and reverse cross-slip agree closely with the experimental measurements. The latter cross-slip stress is a factor of two higher than that of unobstructed planar slip. The model accounts for overlapping dislocation cores and employs a Wigner-Seitz based cell to evaluate misfit energies. By combining ab initio density functional theory (DFT) with anisotropic elasticity, the framework identifies minimum energy pathways for dislocation glide, which can be intermittent and zig-zag. A simplified expression utilizing (π) and Pr Schmid factor ratios is proposed for critical stress corresponding to (π)-to-Pr cross-slip transition. The results are strongly dependent on crystal orientation, underscoring non-Schmid behavior. Overall, this study explores key critical stress parameters essential for informing higher-scale simulations of plasticity in Ti.
{"title":"Cross-slip and easy-glide CRSS in titanium: Theoretical predictions and in-situ TEM measurements","authors":"Tolga Berkay Celebi , Orcun Koray Celebi , Daegun You , Ahmed Sameer Khan Mohammed , Ashley Bucsek , Huseyin Sehitoglu","doi":"10.1016/j.ijplas.2025.104605","DOIUrl":"10.1016/j.ijplas.2025.104605","url":null,"abstract":"<div><div>This study investigates the mechanics of prismatic and first-order pyramidal <span><math><mrow><mo>〈</mo><mi>a</mi><mo>〉</mo></mrow></math></span> slip in titanium (Ti), elucidating the physics of easy-glide and cross-slip through a combination of theory and experiments. Screw-character prismatic (Pr) dislocations in Ti are of particular interest because their complex cores can be stable or unstable, leading to activation by either cross-slip or planar glide. To investigate these mechanisms, site-specific micro tensile samples were prepared using focused ion beam (FIB) milling and mounted on a push-to-pull (PTP) device for in-situ transmission electron microscopy (TEM) tensile testing. The in-situ experiments provide direct observations of the onset of dislocation motion and the precise determination of the critical resolved shear stress (CRSS) for the activated mechanisms, and its evolution with load cycling. A comprehensive theory has been developed to predict the CRSS values for easy glide, cross-slip, and multiplication of dislocations. Predicted critical stresses for pyramidal (π)-to-Pr and reverse cross-slip agree closely with the experimental measurements. The latter cross-slip stress is a factor of two higher than that of unobstructed planar slip. The model accounts for overlapping dislocation cores and employs a Wigner-Seitz based cell to evaluate misfit energies. By combining ab initio density functional theory (DFT) with anisotropic elasticity, the framework identifies minimum energy pathways for dislocation glide, which can be intermittent and zig-zag. A simplified expression utilizing (π) and Pr Schmid factor ratios is proposed for critical stress corresponding to (π)-to-Pr cross-slip transition. The results are strongly dependent on crystal orientation, underscoring non-Schmid behavior. Overall, this study explores key critical stress parameters essential for informing higher-scale simulations of plasticity in Ti.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104605"},"PeriodicalIF":12.8,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894272","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 : 2026-01-01DOI: 10.1016/j.ijplas.2025.104606
Minwoo Park , Deunbom Chung , Wanchuck Woo , Seungcheol Oh , Kyeongjae Jeong , Heung Nam Han
This study proposes an integrated finite element (FE) simulation and convolutional neural network (CNN) model designed for the simultaneous prediction of plastic properties and surface in-plane non-equibiaxial residual stress from spherical indentation responses. By eliminating the need for stress-free reference specimens, the proposed framework enables non-destructive prediction. The framework leverages indentation load-depth curves and directional deformation profiles derived from validated FE simulations. Sensitivity analyses identify the indenter radius and penetration ratio as critical factors for improving prediction accuracy and maximizing the sensitivity of indentation responses to variations in residual stress. The influence of non-equibiaxial residual stress states on indentation behavior is further elucidated through a mechanistic investigation, which reveals a close association with cumulative volumetric changes in equivalent plastic strain near the indentation zone. The CNN training performance supports the sensitivity-based determination of optimal indentation settings. The model is shown to achieve a mean absolute error corresponding to below 5 % on average for residual stresses, while the plasticity parameters are also well captured. Experimental assessment on copper specimens with homogeneous residual stress fields verifies the accuracy and adaptability of the developed FE–CNN model. Further validation using additively manufactured stainless steel, exhibiting complex heterogeneous residual stresses, shows strong consistency with neutron diffraction measurements. This FE–CNN framework presents a robust and scalable approach for comprehensive mechanical characterization, offering substantial benefits for assessing structural integrity and reliability across diverse industrial applications without recourse to destructive testing.
{"title":"Indentation-informed convolutional neural network for simultaneous prediction of non-equibiaxial residual stress and plastic flow","authors":"Minwoo Park , Deunbom Chung , Wanchuck Woo , Seungcheol Oh , Kyeongjae Jeong , Heung Nam Han","doi":"10.1016/j.ijplas.2025.104606","DOIUrl":"10.1016/j.ijplas.2025.104606","url":null,"abstract":"<div><div>This study proposes an integrated finite element (FE) simulation and convolutional neural network (CNN) model designed for the simultaneous prediction of plastic properties and surface in-plane non-equibiaxial residual stress from spherical indentation responses. By eliminating the need for stress-free reference specimens, the proposed framework enables non-destructive prediction. The framework leverages indentation load-depth curves and directional deformation profiles derived from validated FE simulations. Sensitivity analyses identify the indenter radius and penetration ratio as critical factors for improving prediction accuracy and maximizing the sensitivity of indentation responses to variations in residual stress. The influence of non-equibiaxial residual stress states on indentation behavior is further elucidated through a mechanistic investigation, which reveals a close association with cumulative volumetric changes in equivalent plastic strain near the indentation zone. The CNN training performance supports the sensitivity-based determination of optimal indentation settings. The model is shown to achieve a mean absolute error corresponding to below 5 % on average for residual stresses, while the plasticity parameters are also well captured. Experimental assessment on copper specimens with homogeneous residual stress fields verifies the accuracy and adaptability of the developed FE–CNN model. Further validation using additively manufactured stainless steel, exhibiting complex heterogeneous residual stresses, shows strong consistency with neutron diffraction measurements. This FE–CNN framework presents a robust and scalable approach for comprehensive mechanical characterization, offering substantial benefits for assessing structural integrity and reliability across diverse industrial applications without recourse to destructive testing.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104606"},"PeriodicalIF":12.8,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894280","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}
Tailoring composition modulation can be a powerful tool to increase strength and ductility of two- and multicomponent alloys. Here we suggest a model that describes the tensile behavior of alloys with three-dimensional composition undulation. Within the model, the stacking fault energy variation, misfit stresses and dislocation pinning by the inhomogeneous solid solution are considered simultaneously. The model reveals that the composition undulation wavelength that provides peak ultimate strength is determined by a balance of three strengthening mechanisms: 1) dislocation pinning by obstacles, which is enhanced at a small undulation wavelength, 2) resistance to dislocation motion due to stacking fault energy variation, which is highest at a moderate undulation wavelength, and 3) dislocation interaction with misfit stresses, which is most pronounced at a high undulation wavelength. In considering the two latter mechanisms we uncovered a sharp transition from the moderate to the high optimum undulation wavelength at a critical value of the ratio of the misfit to the stacking fault energy variation. The two latter mechanisms increase strength at the expense of reduced ductility and do not affect the product of the ultimate strength and the uniform elongation. In contrast, dislocation pinning by obstacles can increase both strength and ductility due to enhanced strain hardening.
{"title":"Modeling strength and ductility of alloys with intragrain compositional inhomogeneities","authors":"A.M. Smirnov , A.G. Sheinerman , X.T. Li , Z.J. Zhang","doi":"10.1016/j.ijplas.2025.104602","DOIUrl":"10.1016/j.ijplas.2025.104602","url":null,"abstract":"<div><div>Tailoring composition modulation can be a powerful tool to increase strength and ductility of two- and multicomponent alloys. Here we suggest a model that describes the tensile behavior of alloys with three-dimensional composition undulation. Within the model, the stacking fault energy variation, misfit stresses and dislocation pinning by the inhomogeneous solid solution are considered simultaneously. The model reveals that the composition undulation wavelength that provides peak ultimate strength is determined by a balance of three strengthening mechanisms: 1) dislocation pinning by obstacles, which is enhanced at a small undulation wavelength, 2) resistance to dislocation motion due to stacking fault energy variation, which is highest at a moderate undulation wavelength, and 3) dislocation interaction with misfit stresses, which is most pronounced at a high undulation wavelength. In considering the two latter mechanisms we uncovered a sharp transition from the moderate to the high optimum undulation wavelength at a critical value of the ratio of the misfit to the stacking fault energy variation. The two latter mechanisms increase strength at the expense of reduced ductility and do not affect the product of the ultimate strength and the uniform elongation. In contrast, dislocation pinning by obstacles can increase both strength and ductility due to enhanced strain hardening.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104602"},"PeriodicalIF":12.8,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922261","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 : 2025-12-29DOI: 10.1016/j.ijplas.2025.104593
Jin Wang , Nicolas J. Peter , Martin Heilmaier , Ruth Schwaiger
Refractory compositionally complex alloys (RCCAs) are known for their exceptional high-temperature resistance. However, their inherent brittleness at room temperature limits broader practical applications. To explore the effects of microstructure and loading conditions on their deformation behavior, micromechanical experiments, including microbending and micropillar compression tests, were performed on two representative RCCAs: equimolar NbMoCrTiAl (ordered B2 crystal structure) and TaNbHfZrTi (disordered A2 crystal structure). Both alloys demonstrated significant plastic deformation, with strains exceeding 40% at room temperature. Despite prior reports of limited ductility in NbMoCrTiAl at the millimeter scale, our micropillar compression tests on single-crystalline pillars oriented along and reveal substantial plasticity. The dominant deformation mechanisms in NbMoCrTiAl were identified as crystallographic slip and cross-slip of screw dislocations. By contrast, TaNbHfZrTi exhibited a broader range of mechanisms, including screw dislocation slip and a high density of non-screw dislocations, accompanied by kink band formation and activation of high-order slip planes, which collectively contribute to its remarkable ductility among the highest reported for body-centered cubic RCCAs. The atomic size mismatch inherent in compositionally complex alloys enhances dislocation mobility, while the random distribution of elements promotes the formation of edge segments, further improving ductility. These findings highlight the critical role of microstructural characteristics in tailoring the deformation behavior of RCCAs for room-temperature applications.
{"title":"A micromechanical investigation of plasticity in ordered NbMoCrTiAl and disordered TaNbHfZrTi refractory compositionally complex alloys at room temperature","authors":"Jin Wang , Nicolas J. Peter , Martin Heilmaier , Ruth Schwaiger","doi":"10.1016/j.ijplas.2025.104593","DOIUrl":"10.1016/j.ijplas.2025.104593","url":null,"abstract":"<div><div>Refractory compositionally complex alloys (RCCAs) are known for their exceptional high-temperature resistance. However, their inherent brittleness at room temperature limits broader practical applications. To explore the effects of microstructure and loading conditions on their deformation behavior, micromechanical experiments, including microbending and micropillar compression tests, were performed on two representative RCCAs: equimolar NbMoCrTiAl (ordered B2 crystal structure) and TaNbHfZrTi (disordered A2 crystal structure). Both alloys demonstrated significant plastic deformation, with strains exceeding 40% at room temperature. Despite prior reports of limited ductility in NbMoCrTiAl at the millimeter scale, our micropillar compression tests on single-crystalline pillars oriented along <span><math><mrow><mo>〈</mo><mn>1</mn><mspace></mspace><mn>0</mn><mspace></mspace><mn>0</mn><mo>〉</mo></mrow></math></span> and <span><math><mrow><mo>〈</mo><mn>1</mn><mspace></mspace><mn>1</mn><mspace></mspace><mn>0</mn><mo>〉</mo></mrow></math></span> reveal substantial plasticity. The dominant deformation mechanisms in NbMoCrTiAl were identified as crystallographic slip and cross-slip of screw dislocations. By contrast, TaNbHfZrTi exhibited a broader range of mechanisms, including screw dislocation slip and a high density of non-screw dislocations, accompanied by kink band formation and activation of high-order slip planes, which collectively contribute to its remarkable ductility among the highest reported for body-centered cubic RCCAs. The atomic size mismatch inherent in compositionally complex alloys enhances dislocation mobility, while the random distribution of elements promotes the formation of edge segments, further improving ductility. These findings highlight the critical role of microstructural characteristics in tailoring the deformation behavior of RCCAs for room-temperature applications.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104593"},"PeriodicalIF":12.8,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881652","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 : 2025-12-28DOI: 10.1016/j.ijplas.2025.104603
Yufei Chen , Tiwen Lu , Xiyu Chen , Xiaoqi Hu , Ning Yao , Xiaofeng Yang , Haitao Lu , Kaishang Li , Binhan Sun , Yunjie Bi , Xian-Cheng Zhang , Shan-Tung Tu
Additive manufacturing (AM) provides a novel avenue for the fabrication of metal matrix nanocomposites with a uniform distribution of reinforcements and excellent static mechanical properties, while few studies have been conducted on their fatigue behavior. In this study, TiCnp/(CoCrNi)94Al3Ti3 nanocomposites were fabricated using powder bed fusion (PBF), with another representative AM processes-directed energy deposition (DED) as a reference for comparison. In the case of similar low-density defects, though PBF-sample had finer microstructure and higher tensile strength than DED-sample, its fatigue endurance limit (350 MPa) was markedly lower than that of the DED sample (550 MPa). Further investigation revealed that the fatigue initiation sources for DED-samples were pores, while fatigue failure of PBF-samples were mainly initiated from manufactured microcracks. Though the average volume of pores in DED (1.9 × 105 μm3) was significantly larger than microcracks in PBF (1.6 × 104 μm3), the latter posed a more serious threat to fatigue performance. Microcracks were associated with Ti segregation at grain boundaries (GBs) and strong solidification shrinkage, both induced by higher solidification rate of PBF. Finally, two methods were applied to reduce the risk of GB cracking in nanocomposites by adjusting the alloy composition. As a result, segregation at GBs in PBF-fabricated nanocomposites was mitigated, reducing the microcrack density and significantly improving the fatigue resistance. The work reveals the origin of microcrack susceptivity in PBF and offers a microstructural strategy for designing high-strength and fatigue-resistant nanocomposites.
{"title":"Revealing and mitigating the microcrack-sensitive fatigue behavior of laser powder bed fusion fabricated medium-entropy nanocomposites","authors":"Yufei Chen , Tiwen Lu , Xiyu Chen , Xiaoqi Hu , Ning Yao , Xiaofeng Yang , Haitao Lu , Kaishang Li , Binhan Sun , Yunjie Bi , Xian-Cheng Zhang , Shan-Tung Tu","doi":"10.1016/j.ijplas.2025.104603","DOIUrl":"10.1016/j.ijplas.2025.104603","url":null,"abstract":"<div><div>Additive manufacturing (AM) provides a novel avenue for the fabrication of metal matrix nanocomposites with a uniform distribution of reinforcements and excellent static mechanical properties, while few studies have been conducted on their fatigue behavior. In this study, TiC<sub>np</sub>/(CoCrNi)<sub>94</sub>Al<sub>3</sub>Ti<sub>3</sub> nanocomposites were fabricated using powder bed fusion (PBF), with another representative AM processes-directed energy deposition (DED) as a reference for comparison. In the case of similar low-density defects, though PBF-sample had finer microstructure and higher tensile strength than DED-sample, its fatigue endurance limit (350 MPa) was markedly lower than that of the DED sample (550 MPa). Further investigation revealed that the fatigue initiation sources for DED-samples were pores, while fatigue failure of PBF-samples were mainly initiated from manufactured microcracks. Though the average volume of pores in DED (1.9 × 10<sup>5</sup> μm<sup>3</sup>) was significantly larger than microcracks in PBF (1.6 × 10<sup>4</sup> μm<sup>3</sup>), the latter posed a more serious threat to fatigue performance. Microcracks were associated with Ti segregation at grain boundaries (GBs) and strong solidification shrinkage, both induced by higher solidification rate of PBF. Finally, two methods were applied to reduce the risk of GB cracking in nanocomposites by adjusting the alloy composition. As a result, segregation at GBs in PBF-fabricated nanocomposites was mitigated, reducing the microcrack density and significantly improving the fatigue resistance. The work reveals the origin of microcrack susceptivity in PBF and offers a microstructural strategy for designing high-strength and fatigue-resistant nanocomposites.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104603"},"PeriodicalIF":12.8,"publicationDate":"2025-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145844880","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}
Single-phase CoCrNi-based multi-principal element alloys (MPEAs) are recognized for their excellent fatigue damage tolerance. To further enhance their performance, a small amount of Mo was introduced into the CoCrNi system, resulting in the Co35.4Cr22.9Ni35.5Mo6.2 (commercially known as MP35N). This study investigates its tensile and low-cycle fatigue behavior at room temperature. The alloy, with an average grain size of ∼67 µm, exhibits a yield strength of 303 ± 8 MPa, an ultimate tensile strength of 800 ± 7 MPa, and a total-elongation-to-failure of 75 ± 3%. Its pronounced work-hardening and high ductility arise from its low stacking fault energy (SFE), which enables the concurrent activation of planar slip and deformation twinning. Under cyclic loading, the alloy shows pronounced initial cyclic hardening, followed by strain amplitude-dependent responses. Away from fatigue cracks, deformation is governed by planar slip of extended dislocations, whose multiplication and interactions generate sessile stacking-fault nodes and Lomer–Cottrell locks, driving cyclic hardening. At low strain amplitudes (±0.3% and ±0.5%), dislocations remain homogeneously distributed within the grains, with no twinning away from the fatigue cracks. In contrast, at higher strain amplitude (±0.7%), dislocation density increases, accompanied by a growing tendency to rearrange into low-energy structures and localized deformation twinning, as the cyclic peak stresses exceed the critical twinning stress. Surface relief-assisted fatigue cracks predominantly initiate parallel to coherent annealing twin boundaries (ATBs), with fewer occurrences across ATBs, or along/across grain boundaries. This behaviour is governed by slip compatibility and transfer metrics, evaluated through the Taylor factor, elastic stiffness contrast, ATB–loading-axis orientation, Schmid factor, and the Luster–Morris parameter. Near fatigue cracks, high local stresses activate deformation twinning at all strain amplitudes, which is intersected and sheared by shear bands. Twinning contributes to strengthening, while shear bands nucleate within pre-twinned regions, leading to twin bending, necking, detwinning, and the formation of nano-subgrains, which facilitate localized softening. Compared to other CoCrNi-based MPEAs, this Mo-alloyed variant achieves higher peak stresses and comparable or improved fatigue life. These enhancements stem from Mo-induced strengthening and the alloy’s low SFE, which promotes reversible planar slip, suppresses dislocation rearrangement into low-energy structures such as walls, veins, and cells, and amplifies twinning and shear banding near cracks. Collectively, these mechanisms define the overall cyclic stress response, accommodate localised plastic strain, generate tortuous crack paths, and slow crack growth, thereby conferring fatigue resistance that approaches that of dual-phase MPEAs.
{"title":"Superior fatigue response of CoCrNi-based multi-principal element alloy with Mo addition","authors":"Shubham Sisodia , Akshat Godha , Chethan Konkati , Nikhil Suman , Govind Bajargan , Surendra Kumar Makenini , Ankur Chauhan","doi":"10.1016/j.ijplas.2025.104604","DOIUrl":"10.1016/j.ijplas.2025.104604","url":null,"abstract":"<div><div>Single-phase CoCrNi-based multi-principal element alloys (MPEAs) are recognized for their excellent fatigue damage tolerance. To further enhance their performance, a small amount of Mo was introduced into the CoCrNi system, resulting in the Co<sub>35.4</sub>Cr<sub>22.9</sub>Ni<sub>35.5</sub>Mo<sub>6.2</sub> (commercially known as MP35N). This study investigates its tensile and low-cycle fatigue behavior at room temperature. The alloy, with an average grain size of ∼67 µm, exhibits a yield strength of 303 ± 8 MPa, an ultimate tensile strength of 800 ± 7 MPa, and a total-elongation-to-failure of 75 ± 3%. Its pronounced work-hardening and high ductility arise from its low stacking fault energy (SFE), which enables the concurrent activation of planar slip and deformation twinning. Under cyclic loading, the alloy shows pronounced initial cyclic hardening, followed by strain amplitude-dependent responses. Away from fatigue cracks, deformation is governed by planar slip of extended dislocations, whose multiplication and interactions generate sessile stacking-fault nodes and Lomer–Cottrell locks, driving cyclic hardening. At low strain amplitudes (±0.3% and ±0.5%), dislocations remain homogeneously distributed within the grains, with no twinning away from the fatigue cracks. In contrast, at higher strain amplitude (±0.7%), dislocation density increases, accompanied by a growing tendency to rearrange into low-energy structures and localized deformation twinning, as the cyclic peak stresses exceed the critical twinning stress. Surface relief-assisted fatigue cracks predominantly initiate parallel to coherent annealing twin boundaries (ATBs), with fewer occurrences across ATBs, or along/across grain boundaries. This behaviour is governed by slip compatibility and transfer metrics, evaluated through the Taylor factor, elastic stiffness contrast, ATB–loading-axis orientation, Schmid factor, and the Luster–Morris parameter. Near fatigue cracks, high local stresses activate deformation twinning at all strain amplitudes, which is intersected and sheared by shear bands. Twinning contributes to strengthening, while shear bands nucleate within pre-twinned regions, leading to twin bending, necking, detwinning, and the formation of nano-subgrains, which facilitate localized softening. Compared to other CoCrNi-based MPEAs, this Mo-alloyed variant achieves higher peak stresses and comparable or improved fatigue life. These enhancements stem from Mo-induced strengthening and the alloy’s low SFE, which promotes reversible planar slip, suppresses dislocation rearrangement into low-energy structures such as walls, veins, and cells, and amplifies twinning and shear banding near cracks. Collectively, these mechanisms define the overall cyclic stress response, accommodate localised plastic strain, generate tortuous crack paths, and slow crack growth, thereby conferring fatigue resistance that approaches that of dual-phase MPEAs.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104604"},"PeriodicalIF":12.8,"publicationDate":"2025-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922260","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 : 2025-12-26DOI: 10.1016/j.ijplas.2025.104601
Yufeng Song , Lijie Wang , Yuqiang Chen , Wenhui Liu , Ziyi Teng , Qiang Hu , Mingwang Fu
Laminated aluminum alloys (LAAs) are recognized as pivotal materials in aerospace and automotive structures, due to their low density and high specific strength. However, there is an inverse relationship between the strength and plasticity of these alloys, which restricts their further applications in a low-carbon economy. This study proposes the design of micron-scale pure Al interlayers between AA2024/AA7075 layers to inversely strengthen the LAAs by achieving collaborative deformation through interlayer stress gradients and dislocation path modulation, enabling simultaneous enhancement of strength and plasticity. Notably, the micron-layered Al composite (MLAC) exhibits an ultimate tensile strength of 503.4 MPa and elongation of 13.3 %, which are 18.6 % and 29.1 % higher than those of the traditional layered composites (TLACs), significantly surpassing the limitation of the mechanical properties of laminated materials obeying the rule of mixtures (ROM). The underlying strengthening–ductilizing mechanisms are unveiled by in-situ electron backscatter diffraction (EBSD), digital image correlation (DIC), crystal plasticity (CP), and molecular dynamics (MD) based simulations. Results reveal that the strength mismatch between the pure Al layer and the Al alloy layers induces progressive accumulation of soft-layer stress gradient, forming an interfacial stress-affected zone (ISAZs). These zones trigger intricate dislocation-grain interactions and evolve into networked strain bands through the coordinated activation of slip systems. By redistributing local stress fields, these strain bands promote plastic flow as the dominant stress dissipation pathway, dynamically balance interfacial stress concentrations, and induce subcritical microcrack formation, thereby suppressing the tendency for catastrophic brittle fractures. Consequently, these findings establish heterostructure-enabled interlayer design as an effective pathway to achieve strength–ductility synergy in AA2024/AA7075 laminates. The unveiled strengthening–ductilizing mechanism offers a conceptual framework for developing LAAs that transcend conventional mechanical property limitations, obeying ROM.
{"title":"Enhancing the strength and plasticity of laminated aluminum alloy by introducing micron-scale pure aluminum interlayers","authors":"Yufeng Song , Lijie Wang , Yuqiang Chen , Wenhui Liu , Ziyi Teng , Qiang Hu , Mingwang Fu","doi":"10.1016/j.ijplas.2025.104601","DOIUrl":"10.1016/j.ijplas.2025.104601","url":null,"abstract":"<div><div>Laminated aluminum alloys (LAAs) are recognized as pivotal materials in aerospace and automotive structures, due to their low density and high specific strength. However, there is an inverse relationship between the strength and plasticity of these alloys, which restricts their further applications in a low-carbon economy. This study proposes the design of micron-scale pure Al interlayers between AA2024/AA7075 layers to inversely strengthen the LAAs by achieving collaborative deformation through interlayer stress gradients and dislocation path modulation, enabling simultaneous enhancement of strength and plasticity. Notably, the micron-layered Al composite (MLAC) exhibits an ultimate tensile strength of 503.4 MPa and elongation of 13.3 %, which are 18.6 % and 29.1 % higher than those of the traditional layered composites (TLACs), significantly surpassing the limitation of the mechanical properties of laminated materials obeying the rule of mixtures (ROM). The underlying strengthening–ductilizing mechanisms are unveiled by in-situ electron backscatter diffraction (EBSD), digital image correlation (DIC), crystal plasticity (CP), and molecular dynamics (MD) based simulations. Results reveal that the strength mismatch between the pure Al layer and the Al alloy layers induces progressive accumulation of soft-layer stress gradient, forming an interfacial stress-affected zone (ISAZs). These zones trigger intricate dislocation-grain interactions and evolve into networked strain bands through the coordinated activation of slip systems. By redistributing local stress fields, these strain bands promote plastic flow as the dominant stress dissipation pathway, dynamically balance interfacial stress concentrations, and induce subcritical microcrack formation, thereby suppressing the tendency for catastrophic brittle fractures. Consequently, these findings establish heterostructure-enabled interlayer design as an effective pathway to achieve strength–ductility synergy in AA2024/AA7075 laminates. The unveiled strengthening–ductilizing mechanism offers a conceptual framework for developing LAAs that transcend conventional mechanical property limitations, obeying ROM.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104601"},"PeriodicalIF":12.8,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145844912","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 : 2025-12-25DOI: 10.1016/j.ijplas.2025.104600
Ruo-Fei Yuan , Yong Zhang , Yu Zhang , Bo Dong , Yong-Ji Wang , Zhe Zhang , Tang Gu , Yun-Fei Jia , Fu-Zhen Xuan
Harmonic-structured (HS) metallic materials have garnered significant interest owing to their exceptional strength–ductility synergy, yet grain-scale fracture mechanisms remain poorly elucidated, impeding the formulation of predictive strategies for strength–toughness balancing. To address this gap, we fabricated HS CoCrFeMnNi high-entropy alloys with tailored fine-grain (FG) shell fractions. Quasi-in situ tensile experiments monitored via electron backscatter diffraction (EBSD) and crystal plasticity finite element/cohesive zone modeling (CPFEM–CZM) reveal that FG regions exhibit high crack susceptibility due to pronounced strain gradients—particularly at coarse-grain (CG)/FG interfaces and within fine-grained zones—that evolve with strain and intensify stress concentration through deformation incompatibility, thereby promoting preferential crack nucleation and propagation. Conversely, CG regions enable sustained plastic energy dissipation via superior intrinsic deformability. Cracks nucleate and propagate preferentially within FG zones, while CG domains dissipate energy via plasticity and microcracking, diverting energy from primary crack growth. As cracks propagate into CG regions, they activate multiple slip systems, generating strain gradients that increase geometrically necessary dislocation density near crack tips. This elevates back stress, inducing crack blunting and enhancing fracture tolerance. Crucially, an optimal FG fraction (31.4%) prevents premature crack nucleation in FG regions while maintaining strength unattainable in low-FG HS variants, thereby preserving material continuity. This dual-phase synergy ensures superior fracture resistance and strength-toughness balance in HS alloys. Our work elucidates intrinsic fracture resistance mechanisms of HS microstructures and quantifies the effects of FG fraction on damage tolerance, establishing essential microstructural design criteria for advanced metallic materials.
{"title":"Revealing fracture-resistant design principles in harmonic-structured high-entropy alloys using quasi in situ experiments and integrated modeling","authors":"Ruo-Fei Yuan , Yong Zhang , Yu Zhang , Bo Dong , Yong-Ji Wang , Zhe Zhang , Tang Gu , Yun-Fei Jia , Fu-Zhen Xuan","doi":"10.1016/j.ijplas.2025.104600","DOIUrl":"10.1016/j.ijplas.2025.104600","url":null,"abstract":"<div><div>Harmonic-structured (HS) metallic materials have garnered significant interest owing to their exceptional strength–ductility synergy, yet grain-scale fracture mechanisms remain poorly elucidated, impeding the formulation of predictive strategies for strength–toughness balancing. To address this gap, we fabricated HS CoCrFeMnNi high-entropy alloys with tailored fine-grain (FG) shell fractions. Quasi-in situ tensile experiments monitored via electron backscatter diffraction (EBSD) and crystal plasticity finite element/cohesive zone modeling (CPFEM–CZM) reveal that FG regions exhibit high crack susceptibility due to pronounced strain gradients—particularly at coarse-grain (CG)/FG interfaces and within fine-grained zones—that evolve with strain and intensify stress concentration through deformation incompatibility, thereby promoting preferential crack nucleation and propagation. Conversely, CG regions enable sustained plastic energy dissipation via superior intrinsic deformability. Cracks nucleate and propagate preferentially within FG zones, while CG domains dissipate energy via plasticity and microcracking, diverting energy from primary crack growth. As cracks propagate into CG regions, they activate multiple slip systems, generating strain gradients that increase geometrically necessary dislocation density near crack tips. This elevates back stress, inducing crack blunting and enhancing fracture tolerance. Crucially, an optimal FG fraction (31.4%) prevents premature crack nucleation in FG regions while maintaining strength unattainable in low-FG HS variants, thereby preserving material continuity. This dual-phase synergy ensures superior fracture resistance and strength-toughness balance in HS alloys. Our work elucidates intrinsic fracture resistance mechanisms of HS microstructures and quantifies the effects of FG fraction on damage tolerance, establishing essential microstructural design criteria for advanced metallic materials.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104600"},"PeriodicalIF":12.8,"publicationDate":"2025-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145844921","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 : 2025-12-24DOI: 10.1016/j.ijplas.2025.104598
Adrien R. Cassagne , Dimitris C. Lagoudas , Jean-Briac le Graverend
A crystal-plasticity approach with a mean-field framework using a self-consistent approach was developed for complex thermo-mechanical loading in high-temperature shape memory alloys (HTSMAs). More specifically, an implicit scale transition rule called -transition rule was employed. A grain-size-dependent martensitic transformation activation criterion was implemented to offer a smooth transformation hardening behavior as well as a saturating transformation strain magnitude function of the local von Mises stress. Two complex loadings were considered: out-of-phase (OP), consisting of a simultaneous increase of stress and decrease of temperature, and in-phase (IP), consisting of a simultaneous increase of stress and temperature. The material parameters were calibrated using isobaric experiments at different stress levels. This calibration was then used to model complex loading paths to evaluate the relevance of using isobaric parameters for the description of complex paths. Computational results are evaluated based on their capability to reproduce the transformation, actuation, and residual strains experimentally observed for the different loading paths considered. Results show a robustness to predict different loading paths using a set of isobaric calibrated parameters. In-phase paths are described on a purely qualitative basis due to the lack of quantitative experimental data. The model developed can capture the first cycle response shape explained by an initial loading in the self-accommodated martensitic state.
{"title":"A multi-scale modeling of complex thermomechanical loading paths in high-temperature shape memory alloys using a crystal-plasticity framework","authors":"Adrien R. Cassagne , Dimitris C. Lagoudas , Jean-Briac le Graverend","doi":"10.1016/j.ijplas.2025.104598","DOIUrl":"10.1016/j.ijplas.2025.104598","url":null,"abstract":"<div><div>A crystal-plasticity approach with a mean-field framework using a self-consistent approach was developed for complex thermo-mechanical loading in high-temperature shape memory alloys (HTSMAs). More specifically, an implicit scale transition rule called <span><math><mi>β</mi></math></span>-transition rule was employed. A grain-size-dependent martensitic transformation activation criterion was implemented to offer a smooth transformation hardening behavior as well as a saturating transformation strain magnitude function of the local von Mises stress. Two complex loadings were considered: out-of-phase (OP), consisting of a simultaneous increase of stress and decrease of temperature, and in-phase (IP), consisting of a simultaneous increase of stress and temperature. The material parameters were calibrated using isobaric experiments at different stress levels. This calibration was then used to model complex loading paths to evaluate the relevance of using isobaric parameters for the description of complex paths. Computational results are evaluated based on their capability to reproduce the transformation, actuation, and residual strains experimentally observed for the different loading paths considered. Results show a robustness to predict different loading paths using a set of isobaric calibrated parameters. In-phase paths are described on a purely qualitative basis due to the lack of quantitative experimental data. The model developed can capture the first cycle response shape explained by an initial loading in the self-accommodated martensitic state.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104598"},"PeriodicalIF":12.8,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145822856","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}
Accelerating the prediction of mechanical behaviour in heterogenous materials is critical for large-scale microstructure optimization and realizing functionally optimized materials. While existing machine learning approaches have demonstrated an ability to accelerate predictions for the full-field mechanical response of a wide range of heterogenous microstructures, they have been largely limited to monotonic loading conditions. This paper introduces U-PolyConformer, a spatiotemporal machine learning framework that combines U-Net convolutional neural networks with transformer layers, capable of capturing the full-field stress and strain evolution under monotonic and random walk loading conditions. Trained on a large dataset of crystal plasticity finite element method (CPFEM) simulations with FCC polycrystals, the model accurately captures complex phenomena, including strain localization and stress unloading. The U-PolyConformer achieves a 7,900x speed-up over the ground-truth CPFEM simulations while producing high-fidelity results in both interpolative and extrapolative regimes. Comprehensive evaluations demonstrate the U-PolyConformer’s capacity to generalize outside the training distribution to novel microstructures, loading conditions, and strain hardening behaviours. To highlight the model’s potential as a surrogate for accelerating computational materials engineering workflows, a microstructure optimization framework based on static recrystallization is introduced and used to delay the onset of localization. This framework is successfully used to identify the grains which initiate the onset of localization, illustrating how the proposed model and optimization framework may be used for identifying and exploring property-performance relationships.
{"title":"U-PolyConformer: Spatiotemporal machine learning for microstructure engineering","authors":"Dylan Budnick , Benhour Amirian , Abhijit Brahme , Haitham El-Kadiri , Kaan Inal","doi":"10.1016/j.ijplas.2025.104597","DOIUrl":"10.1016/j.ijplas.2025.104597","url":null,"abstract":"<div><div>Accelerating the prediction of mechanical behaviour in heterogenous materials is critical for large-scale microstructure optimization and realizing functionally optimized materials. While existing machine learning approaches have demonstrated an ability to accelerate predictions for the full-field mechanical response of a wide range of heterogenous microstructures, they have been largely limited to monotonic loading conditions. This paper introduces U-PolyConformer, a spatiotemporal machine learning framework that combines U-Net convolutional neural networks with transformer layers, capable of capturing the full-field stress and strain evolution under monotonic and random walk loading conditions. Trained on a large dataset of crystal plasticity finite element method (CPFEM) simulations with FCC polycrystals, the model accurately captures complex phenomena, including strain localization and stress unloading. The U-PolyConformer achieves a 7,900x speed-up over the ground-truth CPFEM simulations while producing high-fidelity results in both interpolative and extrapolative regimes. Comprehensive evaluations demonstrate the U-PolyConformer’s capacity to generalize outside the training distribution to novel microstructures, loading conditions, and strain hardening behaviours. To highlight the model’s potential as a surrogate for accelerating computational materials engineering workflows, a microstructure optimization framework based on static recrystallization is introduced and used to delay the onset of localization. This framework is successfully used to identify the grains which initiate the onset of localization, illustrating how the proposed model and optimization framework may be used for identifying and exploring property-performance relationships.</div></div>","PeriodicalId":340,"journal":{"name":"International Journal of Plasticity","volume":"197 ","pages":"Article 104597"},"PeriodicalIF":12.8,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145822859","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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