傾角粒界を有する純銅双結晶の1パスECAP加工における粒界方位差の変化

摘要

強ひずみ加工(severe plastic deformation:SPD)における超微細粒組織への形成過程とその微細化メカニズムに関する研究が多く報告されている，これらの報告の多くは変形初期に小角粒界が粒内に形成されて，その後ひずみの増加と共に方位差が増加するといういわゆる"grain subdivision"機構を超微細粒組織の形成機構として明示的または暗示的に支持している.%Grain boundaries can change their misorientation by absorbing lattice dislocations at relatively high temperature under moderate straining. The same phenomenon is believed to occur during severe plastic deformation down to room temperature leaving grain boundaries in the nonequilibrium state. Direct evidence of dynamic misorientation change of the grain boundary during severe plastic deformation was obtained in copper bicrystals subjected to equal-channel angular pressing (ECAP) for one pass. Marked dependence of misorientaion change on the initial orientation was revealed, and is associated with the unique slip patterns of ECAP, where the shear deformation is restricted to the narrow zone parallel to the intersecting plane of the two channels. The degree of change can be related to slip geometry in terms of grain boundary plane orientation.