大塑性变形过程中单晶和多晶铜的组织演变及变形机理研究

Microstructural Evolution and Deformation Mechanism during Large Elastic-Plastic Deformation for Single Crystal and Polycrystalline Copper

用等通道转角挤压(equal channel angular pressing,ECAP)法对单晶铜和多晶铜进行了多道次的挤压变形,对挤压过程中晶粒细化机理和变形机理进行了分析。结果表明,单晶铜和多晶铜在A路径下变形8道次以后,晶粒平均尺寸达到5μm以下,但在4道次以后单晶铜沿挤压方向出现织构,多晶铜中出现均匀的等轴晶。TEM分析认为,晶粒位相差随剪切变形量的增加而增大,ECAP加工后材料内部大角度晶界数的增加导致了变形机制的改变,晶界滑移导致了晶粒转动趋势的增加。在多道次挤压后,单晶铜和多晶铜材料的微观结构特征是含有高密度位错的大角度晶界等轴晶组织,以及晶界上的非平衡结构。

The microstructural evolution and the mechanical response of monocrystal and polycrystal copper subjected to severe plastic deformation using equal channel angular pressing （ECAP） were investigated. Results indicated that the average grain size was less than 5μm after eight passes under route A. After four passes pinch, it appears texture along the direction of extrusion in monocrystal copper and homogeneous equiaxed grains form in polycrystal copper. By TEM analysis, the phase difference of high angle grain boundary increases with the increase of shear deformation, the high angle boundary of material interior causes the mechanical transformation and grain boundary sliding causes the increase of grain turning tendency. The microscopic structure and feature after multipass in monocrystal and polycrystal copper are high angle grain boundary containing high-density dislocation and non-equilibrium structure along grain boundaries.