Realizing the greater potential for precipitation strengthening in nanograined alloys is highly desirable but often challenging.In this study,an Fe-Ni based alloy was subjected to plastic deformation followed by aging...Realizing the greater potential for precipitation strengthening in nanograined alloys is highly desirable but often challenging.In this study,an Fe-Ni based alloy was subjected to plastic deformation followed by aging treatment to further strengthen nanograins through high-density precipitates.Microstructural characterization showed that nanograins account for∼64%of the volume,with an average size of 44 nm.Notably,the nanoprecipitates in the nanograins exhibit utterly different characteristics from those in the coarse grains.As a result,the sample has an ultra-high yield strength of 1677 MPa.Further analyses indicated that the D0_(24)-structured nanoprecipitates at the nanograin boundaries provide a greater precipitation strengthening than conventional L1_(2)-structured nanoprecipitates within the coarse grains,the reason of which is that the precipitates inhibit partial dislocation emission and grain boundary migration of the nanograins.This work deepens the understanding of precipitation strengthening in nanograined materials and proposes a novel strategy to further strengthen nanograined alloys.展开更多
A nanotwinned 316 L austenitic stainless steel was prepared by means of surface mechanical grinding treatment.After recovery annealing,the density of dislocations decreases obviously while the average twin/matrix lame...A nanotwinned 316 L austenitic stainless steel was prepared by means of surface mechanical grinding treatment.After recovery annealing,the density of dislocations decreases obviously while the average twin/matrix lamella thickness still keeps in the nanometer scale.The annealed nanotwinned sample exhibits a high tensile yield strength of 771 MPa and a considerate uniform elongation of 8%.TEM observations showed that accommodating more dislocations and secondary twinning inside the nanotwins contribute to the enhanced ductility and work hardening rate of the annealed nanotwinned sample.展开更多
The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,th...The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,the precipitation of Cr at nanometer scale provided further strengthening and brought substantial recovery of electrical conductivity.The aged nanostructured CuCrZr alloy exhibited a high tensile strength of 832MPa and a high electrical conductivity of 71.2%IACS.The details of precipitation tuned by nanotwin boundaries were demonstrated in this work.The combined strengthening of nanostructures and nanoprecipitates was discussed.展开更多
Lamellar nanostructures were induced in a plain martensitic low-carbon steel by using dynamic plastic deformation at room temperature.The nanostructured steel was hardened after annealing at 673 K for20 min,with a ten...Lamellar nanostructures were induced in a plain martensitic low-carbon steel by using dynamic plastic deformation at room temperature.The nanostructured steel was hardened after annealing at 673 K for20 min,with a tensile strength increased from 1.2 GPa to 1.6 GPa.Both the remained nanostructures and annealing-induced precipitates in nano-scale play key roles in the hardening.展开更多
The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation ...The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation to the surface layer. The subsequent nitriding kinetics of the as-treated samples with the nanostructured surface layer is greatly enhanced so that the nitriding temperatures can be reduce to 300 - 400 °C regions. This enhanced processing method demonstrates both the technological significance of nanomaterials in advancing the traditional processing techniques, and provides a new approach for selective surface reactions in solids. This article reviews the present state of the art in this field. The microstructure and properties of SMAT samples nitrided will be summarized. Further considerations of the development and applications of this new technique will also be presented.展开更多
Cu single crystals were subjected to dynamic compression plastic deformation to investigate orientation- dependent twinning. The experimental results showed that twinning is closely related to the ratio of the maximum...Cu single crystals were subjected to dynamic compression plastic deformation to investigate orientation- dependent twinning. The experimental results showed that twinning is closely related to the ratio of the maximum Schmid factor for twinning partial （mt） to the maximum Schmid factor for perfect dislocation （ms）, i.e., mT/ms, rather than roT. The twin volume fraction VT increases with the rot/ms value and the most favorable orientation for twinning has the maximum roT/ms value （1.15）. The relationships of roT/ms with both effective stacking fault energy γeff and threshold stress for twinning TT were established for under- standing orientation-dependent twinning. Further insights into the orientation-dependent twinning and guidance for developing bulk high density nanotwinned materials are provided.展开更多
基金support from the National Natural Science Foundation(No.52473339).
文摘Realizing the greater potential for precipitation strengthening in nanograined alloys is highly desirable but often challenging.In this study,an Fe-Ni based alloy was subjected to plastic deformation followed by aging treatment to further strengthen nanograins through high-density precipitates.Microstructural characterization showed that nanograins account for∼64%of the volume,with an average size of 44 nm.Notably,the nanoprecipitates in the nanograins exhibit utterly different characteristics from those in the coarse grains.As a result,the sample has an ultra-high yield strength of 1677 MPa.Further analyses indicated that the D0_(24)-structured nanoprecipitates at the nanograin boundaries provide a greater precipitation strengthening than conventional L1_(2)-structured nanoprecipitates within the coarse grains,the reason of which is that the precipitates inhibit partial dislocation emission and grain boundary migration of the nanograins.This work deepens the understanding of precipitation strengthening in nanograined materials and proposes a novel strategy to further strengthen nanograined alloys.
基金Financial support from the National Natural Science Foundation of China(Grant No.51771196)the National Key R&D Program of China(Grant No.2017YFA0204401 and No.2017YFA0204402)the Key Research Program of Frontier Science,Chinese Academy of Sciences。
文摘A nanotwinned 316 L austenitic stainless steel was prepared by means of surface mechanical grinding treatment.After recovery annealing,the density of dislocations decreases obviously while the average twin/matrix lamella thickness still keeps in the nanometer scale.The annealed nanotwinned sample exhibits a high tensile yield strength of 771 MPa and a considerate uniform elongation of 8%.TEM observations showed that accommodating more dislocations and secondary twinning inside the nanotwins contribute to the enhanced ductility and work hardening rate of the annealed nanotwinned sample.
基金supported by the Ministry of Science&Technology of China(No.2017YFA0204401)the Chinese Academy of Sciences(No.zdyz201701)+3 种基金the Liaoning Revitalization Talents Program(No.XLYC1808008)the National Natural Science Foundation of China(Nos.51501192 and 51771196)the Fundamental Research Funds for the Central Universities(No.3072019CF1017)the Key Research Program of Frontier Science,Chinese Academy of Sciences.
文摘The mixed nanostructure mainly consisting of nanotwins and nanograins was obtained in a solid solution CuCrZr alloy by means of dynamic plastic deformation at cryogenic temperature.After subsequent aging treatments,the precipitation of Cr at nanometer scale provided further strengthening and brought substantial recovery of electrical conductivity.The aged nanostructured CuCrZr alloy exhibited a high tensile strength of 832MPa and a high electrical conductivity of 71.2%IACS.The details of precipitation tuned by nanotwin boundaries were demonstrated in this work.The combined strengthening of nanostructures and nanoprecipitates was discussed.
基金Financial supports from the National Basic Research Program of China(Grant No.2012CB932201)the National Natural Science Foundation of China(Grant No.51371172)+1 种基金Bosch (China) Investment Ltd.,the MOST of China(2010DFB54010)the CAS International Cooperation Project(GJHZ1033)
文摘Lamellar nanostructures were induced in a plain martensitic low-carbon steel by using dynamic plastic deformation at room temperature.The nanostructured steel was hardened after annealing at 673 K for20 min,with a tensile strength increased from 1.2 GPa to 1.6 GPa.Both the remained nanostructures and annealing-induced precipitates in nano-scale play key roles in the hardening.
基金supported by NSF of China(Grants No.50021101)Ministry of Science&Technology of China(G1999064505).
文摘The microstructure in the surface layer of iron and steel samples can be refined at the nanometer scale by means of a surface mechanical attrition treatment (SMAT) that generates repetitive severe plastic deformation to the surface layer. The subsequent nitriding kinetics of the as-treated samples with the nanostructured surface layer is greatly enhanced so that the nitriding temperatures can be reduce to 300 - 400 °C regions. This enhanced processing method demonstrates both the technological significance of nanomaterials in advancing the traditional processing techniques, and provides a new approach for selective surface reactions in solids. This article reviews the present state of the art in this field. The microstructure and properties of SMAT samples nitrided will be summarized. Further considerations of the development and applications of this new technique will also be presented.
基金Financial supports from the National Natural Science Foundation of China(Grant No.51371172)the Ministry of Science and Technology of People’s Republic of China(Grant No.2012CB932201)
文摘Cu single crystals were subjected to dynamic compression plastic deformation to investigate orientation- dependent twinning. The experimental results showed that twinning is closely related to the ratio of the maximum Schmid factor for twinning partial （mt） to the maximum Schmid factor for perfect dislocation （ms）, i.e., mT/ms, rather than roT. The twin volume fraction VT increases with the rot/ms value and the most favorable orientation for twinning has the maximum roT/ms value （1.15）. The relationships of roT/ms with both effective stacking fault energy γeff and threshold stress for twinning TT were established for under- standing orientation-dependent twinning. Further insights into the orientation-dependent twinning and guidance for developing bulk high density nanotwinned materials are provided.
