A two-dimensional discrete dislocation dynamics （DDD） technology by Giessen and Needleman （1995）, which has been extended by integrating a dislocation-grain boundary interaction model, is used to computationally a...A two-dimensional discrete dislocation dynamics （DDD） technology by Giessen and Needleman （1995）, which has been extended by integrating a dislocation-grain boundary interaction model, is used to computationally analyze the micro-cyclic plastic response of polycrystals containing micron-sized grains, with special attentions to significant influence of dislocationpenetrable grain boundaries （GBs） on the micro-plastic cyclic responses of polycrystals and underlying dislocation mechanism. Toward this end, a typical polycrystalline rectangular specimen under simple tension-compression loading is considered. Results show that, with the increase of cycle accumulative strain, continual dislocation accumulation and enhanced dislocation-dislocation interactions induce the cyclic hardening behavior; however, when a dynamic balance among dislocation nucleation, penetration through GB and dislocation annihilation is approximately established, cyclic stress gradually tends to saturate. In addition, other factors, including the grain size, cyclic strain amplitude and its history, also have considerable influences on the cyclic hardening and saturation.展开更多
There is an increasing trend for producing copper-containing steels, with copper being either a residual element from scraps or an intentional addition, i. e. , in weathering steel. The issue of surface hot shortness ...There is an increasing trend for producing copper-containing steels, with copper being either a residual element from scraps or an intentional addition, i. e. , in weathering steel. The issue of surface hot shortness occurs during the hot working of steels containing copper, and a significant amount of work has been performed on this topic. This paper provides a review of related studies on this phenomenon. The formation mechanism, as analyzed, is the liquid metal embrittlement caused by the liquid copper penetration into austenite grain boundaries at the metal surface, where the copper originates from the selective oxidation of the steel at high temperature. On the basis of the mechanism, more importance is placed on analyzing the effect on the phenomenon by varying the controlling factors, including the heating process, alloying additions, and deformation conditions. Possible solutions to the problem are finalized, and some further work must be performed in the future.展开更多
基金supported by the National Natural Science Foundation of China(No.10672064).
文摘A two-dimensional discrete dislocation dynamics （DDD） technology by Giessen and Needleman （1995）, which has been extended by integrating a dislocation-grain boundary interaction model, is used to computationally analyze the micro-cyclic plastic response of polycrystals containing micron-sized grains, with special attentions to significant influence of dislocationpenetrable grain boundaries （GBs） on the micro-plastic cyclic responses of polycrystals and underlying dislocation mechanism. Toward this end, a typical polycrystalline rectangular specimen under simple tension-compression loading is considered. Results show that, with the increase of cycle accumulative strain, continual dislocation accumulation and enhanced dislocation-dislocation interactions induce the cyclic hardening behavior; however, when a dynamic balance among dislocation nucleation, penetration through GB and dislocation annihilation is approximately established, cyclic stress gradually tends to saturate. In addition, other factors, including the grain size, cyclic strain amplitude and its history, also have considerable influences on the cyclic hardening and saturation.
文摘There is an increasing trend for producing copper-containing steels, with copper being either a residual element from scraps or an intentional addition, i. e. , in weathering steel. The issue of surface hot shortness occurs during the hot working of steels containing copper, and a significant amount of work has been performed on this topic. This paper provides a review of related studies on this phenomenon. The formation mechanism, as analyzed, is the liquid metal embrittlement caused by the liquid copper penetration into austenite grain boundaries at the metal surface, where the copper originates from the selective oxidation of the steel at high temperature. On the basis of the mechanism, more importance is placed on analyzing the effect on the phenomenon by varying the controlling factors, including the heating process, alloying additions, and deformation conditions. Possible solutions to the problem are finalized, and some further work must be performed in the future.
