The Nb single crystals of both[321]and[110]orientations have been cyclicly deformed in tension-compression at constant strain rate 8×10^(-4)s^(-1)over a range of plastic strain amplitudes between 10^(-3)and 10^(-...The Nb single crystals of both[321]and[110]orientations have been cyclicly deformed in tension-compression at constant strain rate 8×10^(-4)s^(-1)over a range of plastic strain amplitudes between 10^(-3)and 10^(-4).The cyclic hardening,the changes in shape of crystals and the asymmetry of stress have been studied.The hardening curve can be divided into three stages,i.e.first,rapid-hardening and saturated stage. In the first stage of cyclic hardening curve dominant features of dislocation configura- tions are high density networks and debris loops.In the rapid-hardening stage the main fea- ture is the formation of dislocation bundles.In the saturated a well defined bundle structure fully develops and between them it is filled with only screw dislocations and the imposed strain is accommodated mainly by the motion of screw dislocations travelling to and from between the bundles.Three-dimension cell,two-dimension cell or bundle structures are summarized as the saturated structures of bcc metals.展开更多
The slip behavior and mechanism of large-size Mo-3Nb single crystal have been investigated and disclosed comprehensively at room temperature by quasi-static compression with various strains.With the increase of deform...The slip behavior and mechanism of large-size Mo-3Nb single crystal have been investigated and disclosed comprehensively at room temperature by quasi-static compression with various strains.With the increase of deformation,the slip traces change from shallow non-uniform slip lines to dense and uniform slip bands.Different slip traces in the same deformation condition were observed,suggesting that the slip traces in the single crystal are controlled by different types and arrangement mechanisms of mobile dislocation.To clarify the relationship between slip behavior and dislocation arrangement,TEM and AFM analyses were performed.Significant discrepancy between the mobility of screw segments and edge segments caused by double cross-slip multiplication mechanism is the reason why different slip features were witnessed.During the whole slip deformation process,screw dislocations play a dominant role and they are inclined to form wall-substructures by interaction and entanglement.With the development of dislocation accumulation,the entangled dislocation walls evolve into dislocation cells with higher stability.展开更多
文摘The Nb single crystals of both[321]and[110]orientations have been cyclicly deformed in tension-compression at constant strain rate 8×10^(-4)s^(-1)over a range of plastic strain amplitudes between 10^(-3)and 10^(-4).The cyclic hardening,the changes in shape of crystals and the asymmetry of stress have been studied.The hardening curve can be divided into three stages,i.e.first,rapid-hardening and saturated stage. In the first stage of cyclic hardening curve dominant features of dislocation configura- tions are high density networks and debris loops.In the rapid-hardening stage the main fea- ture is the formation of dislocation bundles.In the saturated a well defined bundle structure fully develops and between them it is filled with only screw dislocations and the imposed strain is accommodated mainly by the motion of screw dislocations travelling to and from between the bundles.Three-dimension cell,two-dimension cell or bundle structures are summarized as the saturated structures of bcc metals.
基金financially supported by the Major Science and Technology Project of Shaanxi Province,China(No.2020zdzx04-02-02)the Key Research and Development Program of Shaanxi,China(Nos.2019ZDLGY05-04 and 2019ZDLGY05-06)the National key Research and Development Program(No.2017YFB0306003)。
文摘The slip behavior and mechanism of large-size Mo-3Nb single crystal have been investigated and disclosed comprehensively at room temperature by quasi-static compression with various strains.With the increase of deformation,the slip traces change from shallow non-uniform slip lines to dense and uniform slip bands.Different slip traces in the same deformation condition were observed,suggesting that the slip traces in the single crystal are controlled by different types and arrangement mechanisms of mobile dislocation.To clarify the relationship between slip behavior and dislocation arrangement,TEM and AFM analyses were performed.Significant discrepancy between the mobility of screw segments and edge segments caused by double cross-slip multiplication mechanism is the reason why different slip features were witnessed.During the whole slip deformation process,screw dislocations play a dominant role and they are inclined to form wall-substructures by interaction and entanglement.With the development of dislocation accumulation,the entangled dislocation walls evolve into dislocation cells with higher stability.
