Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity ca...Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity caused by heterogeneous structures in the magnesium matrix composite remains unclear.In this study,a dual-heterogeneous TiC/AZ61 composite exhibits significantly improved plastic elongation(PEL)by nearly one time compared to uniform FG composite,meanwhile maintaining a high strength(UTS:417 MPa).This is because more severe deformation inhomogeneity in heterogeneous structure leads to more geometrically necessary dislocations(GNDs)accumulation and stronger HDI stress,resulting in higher HDI hardening compared to FG and CG composites.During the early stage of plastic deformation,the pile-up types of GND in the FG zone and CG zone are significantly different.GNDs tend to form substructures in the FG zone instead of the CG zone.They only accumulate at grain boundaries of the CG region,thereby leading to obviously increased back stress in the CG region.In the late deformation stage,the elevated HDI stress activates the new〈c+a〉dislocations in the CG region,resulting in dislocation entanglements and even the formation of substructures,further driving the high hardening in the heterogeneous composite.However,For CG composite,〈c+a〉dislocations are not activated even under large plastic strains,and only〈a〉dislocations pile up at grain boundaries and twin boundaries.Our work provides an in-depth understanding of dislocation variation and HDI hardening in heterogeneous magnesium-based composites.展开更多
The grain-scale tension-compression(T-C)asymmetric slip behavior and geometrically necessary dislocation(GND)density in an aged and twin-free Mg-10Y sheet were statistically studied using slip trace analysis and elect...The grain-scale tension-compression(T-C)asymmetric slip behavior and geometrically necessary dislocation(GND)density in an aged and twin-free Mg-10Y sheet were statistically studied using slip trace analysis and electron backscatter diffraction(EBSD)analysis.A significantly asymmetric slip activity,i.e.,higher tensile slip activity and proportion of non-basal slip,was manifested.Prismatic〈a〉(37.1%)and basal〈a〉(27.6%)slips dominated the tensile deformation,followed by pyramidalⅡ〈c+a〉slip(20.0%).While during compression,basal〈a〉slip(61.9%)was the most active slip mode,and only 6.9% pyramidalⅡ〈c+a〉slip was observed.The critical resolved shear stress(CRSS)ratio was estimated based on~800 sets of the identified slip traces,which suggested that the CRSS_(pyrⅡ)/CRSS_(bas)for compression was~3 times than that of tension.The pyramidalⅡ〈c+a〉slip was more active when the slip plane was under tension than under compression,which was consistent with the calculated asymmetric CRSS_(pyrⅡ)/CRSS_(bas).The activity of multiple slip,cross slip and slip transfer,as well as the GND density were also T-C asymmetric.This work thoughtfully demonstrated the T-C asymmetric slip behavior and plastic heterogeneity in Mg alloys which was believed to be responsible for the macroscopic T-C asymmetry when twinning was absent.The present statistical results are valuable for validating and/or facilitating crystal plasticity simulations.展开更多
1060/7050 Al/Al laminated metal composites(LMCs)with heterogeneous lamellar structures were prepared by accumulative roll bonding(ARB),cold rolling and subsequent annealing treatment.The strengthening mechanism was in...1060/7050 Al/Al laminated metal composites(LMCs)with heterogeneous lamellar structures were prepared by accumulative roll bonding(ARB),cold rolling and subsequent annealing treatment.The strengthening mechanism was investigated by microstructural characterization,mechanical property tests and in-situ fracture morphology observations.The results show that microstructural differences between the constituent layers are present in the Al/Al LMCs after various numbers of ARB cycles.Compared with rolled 2560-layered Al/Al LMCs with 37.5%and 50.0%rolling reductions,those with 62.5%rolling reductions allow for more effective improvements in the mechanical properties after annealing treatment due to their relatively high mechanical incompatibility across the interface.During tensile deformation,with the increased magnitude of incompatibility in the 2560-layered Al/Al LMC with a heterogeneous lamellar structure,the densities of the geometrically necessary dislocations(GNDs)increase to accommodate the relatively large strain gradient,resulting in considerable back stress strengthening and improved mechanical properties.展开更多
基金support from the National Natural Science Foundation of China(No:52061040)China Postdoctoral Science Foundation(No:2021M692512)+1 种基金Opening Project of Material Corrosion and Protection Key Laboratory of Sichuan Province(No:2023CL01)Open Projects of Key Laboratory of Advanced Technologies of Materials,Ministry of Education China,Southwest Jiaotong University(No:KLATM202003).
文摘Integrating a heterogeneous structure can significantly enhance the strength-ductility synergy of composites.However,the relationship between hetero-deformation induced(HDI)strain hardening and dislocation activity caused by heterogeneous structures in the magnesium matrix composite remains unclear.In this study,a dual-heterogeneous TiC/AZ61 composite exhibits significantly improved plastic elongation(PEL)by nearly one time compared to uniform FG composite,meanwhile maintaining a high strength(UTS:417 MPa).This is because more severe deformation inhomogeneity in heterogeneous structure leads to more geometrically necessary dislocations(GNDs)accumulation and stronger HDI stress,resulting in higher HDI hardening compared to FG and CG composites.During the early stage of plastic deformation,the pile-up types of GND in the FG zone and CG zone are significantly different.GNDs tend to form substructures in the FG zone instead of the CG zone.They only accumulate at grain boundaries of the CG region,thereby leading to obviously increased back stress in the CG region.In the late deformation stage,the elevated HDI stress activates the new〈c+a〉dislocations in the CG region,resulting in dislocation entanglements and even the formation of substructures,further driving the high hardening in the heterogeneous composite.However,For CG composite,〈c+a〉dislocations are not activated even under large plastic strains,and only〈a〉dislocations pile up at grain boundaries and twin boundaries.Our work provides an in-depth understanding of dislocation variation and HDI hardening in heterogeneous magnesium-based composites.
基金supported by the National Natural Science Foundation of China(No.52171125)the Sichuan Science and Technology Program(No.2024NSFSC0193)。
文摘The grain-scale tension-compression(T-C)asymmetric slip behavior and geometrically necessary dislocation(GND)density in an aged and twin-free Mg-10Y sheet were statistically studied using slip trace analysis and electron backscatter diffraction(EBSD)analysis.A significantly asymmetric slip activity,i.e.,higher tensile slip activity and proportion of non-basal slip,was manifested.Prismatic〈a〉(37.1%)and basal〈a〉(27.6%)slips dominated the tensile deformation,followed by pyramidalⅡ〈c+a〉slip(20.0%).While during compression,basal〈a〉slip(61.9%)was the most active slip mode,and only 6.9% pyramidalⅡ〈c+a〉slip was observed.The critical resolved shear stress(CRSS)ratio was estimated based on~800 sets of the identified slip traces,which suggested that the CRSS_(pyrⅡ)/CRSS_(bas)for compression was~3 times than that of tension.The pyramidalⅡ〈c+a〉slip was more active when the slip plane was under tension than under compression,which was consistent with the calculated asymmetric CRSS_(pyrⅡ)/CRSS_(bas).The activity of multiple slip,cross slip and slip transfer,as well as the GND density were also T-C asymmetric.This work thoughtfully demonstrated the T-C asymmetric slip behavior and plastic heterogeneity in Mg alloys which was believed to be responsible for the macroscopic T-C asymmetry when twinning was absent.The present statistical results are valuable for validating and/or facilitating crystal plasticity simulations.
基金financial support from the Special Fund for Special Posts of Guizhou University,China(No.[2022]06)the Guizhou Provincial Basic Research Program(Natural Science),China(No.ZK[2023]78)+1 种基金the National Natural Science Foundation of China(No.52365020)the Open Fund Project of Key Laboratory of Advanced Manufacturing Technology,China(No.GZUAMT2022KF[04]).
文摘1060/7050 Al/Al laminated metal composites(LMCs)with heterogeneous lamellar structures were prepared by accumulative roll bonding(ARB),cold rolling and subsequent annealing treatment.The strengthening mechanism was investigated by microstructural characterization,mechanical property tests and in-situ fracture morphology observations.The results show that microstructural differences between the constituent layers are present in the Al/Al LMCs after various numbers of ARB cycles.Compared with rolled 2560-layered Al/Al LMCs with 37.5%and 50.0%rolling reductions,those with 62.5%rolling reductions allow for more effective improvements in the mechanical properties after annealing treatment due to their relatively high mechanical incompatibility across the interface.During tensile deformation,with the increased magnitude of incompatibility in the 2560-layered Al/Al LMC with a heterogeneous lamellar structure,the densities of the geometrically necessary dislocations(GNDs)increase to accommodate the relatively large strain gradient,resulting in considerable back stress strengthening and improved mechanical properties.
