Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,her...Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast imaging.The results indicate that hydrogen can strongly affect dislocation activities.In detail,hydrogen can promote the formation of stacking faults with a long dissociation distance.Besides,dislocation movements are frequently observed during hydrogen desorption.The required resolved shear stress is considered to be the residual stresses rendered by hydrogen segregation.Furthermore,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.展开更多
Heterostructures of alloyed composites,comprising heterogeneous domains with dramatically different constitutive properties,hold remarkable potential to expand the realm of material design systems and resolve the trad...Heterostructures of alloyed composites,comprising heterogeneous domains with dramatically different constitutive properties,hold remarkable potential to expand the realm of material design systems and resolve the tradeoffbetween strength and ductility.This study introduces an innovative materials design method for synthesizing gradient pseudo-precipitates heterostructure(GPHS)in non-heat-treatable Al-2.5%Mg alloys.Utilizing cost-effective mild steel as both the diffusion source and protective layer,this heterostructure is achieved through pin-less friction stir-assisted cyclic localized deformation process.Exogenous Fe atoms diffuse across the interface by friction stir-induced heat conduction,forming Fe-Al second-phase particles in the Al alloy matrix.A rapid inter-diffusion mechanism is activated in conjunction with dense dislocation walls,grain boundaries,and sub-structures,resulting in the formation of pseudo-precipitates.These pseudo-precipitates are ultimately dispersed in a gradient distribution throughout the entire thickness of the Al alloy matrix induced by localized incremental deformation.The GPHSed Al-2.5%Mg alloy exhibits an enhanced synergy of strength and ductility,with a uniform elongation increase from 11%to 21.2%,while maintaining the strength.Multiple strengthening and hardening mechanisms,such as solid solution strengthening,dislocation hardening,and second phase strengthening,work synergistically to promote mechanical performance.Notably,the hetero-deformation between hard pseudo-precipitates and soft Al alloy matrix induces additional strain hardening,leading to high ductility.This work provides a fresh perspective on the design and fabrication of high-performance alloys with advanced heterostructures,especially for non-heat-treatable alloys.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(No.52101022)the Shaanxi Province Natural Science Foundation(No.2021JQ-080).
文摘Hydrogen embrittlement(HE)poses a significant challenge for the development of high-strength metallic materials.However,explanations for the observed HE phenomena are still under debate.To shed light on this issue,here we investigated the hydrogen-defect interaction by comparing the dislocation structure evolution after hydrogen adsorption and desorption in a Fe-28Mn-0.3C(wt%)twinning-induced plasticity steel with an austenitic structure using in situ electron channeling contrast imaging.The results indicate that hydrogen can strongly affect dislocation activities.In detail,hydrogen can promote the formation of stacking faults with a long dissociation distance.Besides,dislocation movements are frequently observed during hydrogen desorption.The required resolved shear stress is considered to be the residual stresses rendered by hydrogen segregation.Furthermore,the microstructural heterogeneity could lead to the discrepancy of dislocation activities even within the same materials.
基金financial support from the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIP)(Nos.NRF-2021R1A2C3006662 and NRF-2022R1A5A1030054)supported by Brain Pool Program through the National Research Foundation of Korea(NRF-RS202300263999).
文摘Heterostructures of alloyed composites,comprising heterogeneous domains with dramatically different constitutive properties,hold remarkable potential to expand the realm of material design systems and resolve the tradeoffbetween strength and ductility.This study introduces an innovative materials design method for synthesizing gradient pseudo-precipitates heterostructure(GPHS)in non-heat-treatable Al-2.5%Mg alloys.Utilizing cost-effective mild steel as both the diffusion source and protective layer,this heterostructure is achieved through pin-less friction stir-assisted cyclic localized deformation process.Exogenous Fe atoms diffuse across the interface by friction stir-induced heat conduction,forming Fe-Al second-phase particles in the Al alloy matrix.A rapid inter-diffusion mechanism is activated in conjunction with dense dislocation walls,grain boundaries,and sub-structures,resulting in the formation of pseudo-precipitates.These pseudo-precipitates are ultimately dispersed in a gradient distribution throughout the entire thickness of the Al alloy matrix induced by localized incremental deformation.The GPHSed Al-2.5%Mg alloy exhibits an enhanced synergy of strength and ductility,with a uniform elongation increase from 11%to 21.2%,while maintaining the strength.Multiple strengthening and hardening mechanisms,such as solid solution strengthening,dislocation hardening,and second phase strengthening,work synergistically to promote mechanical performance.Notably,the hetero-deformation between hard pseudo-precipitates and soft Al alloy matrix induces additional strain hardening,leading to high ductility.This work provides a fresh perspective on the design and fabrication of high-performance alloys with advanced heterostructures,especially for non-heat-treatable alloys.
