强塑性循环变形中单晶铜和多晶铜的力学性能

Mechanical properties of single crystal copper and polycrystalline copper during super plastic and cyclic deformation

分别用小通道角模具(模具Ⅰ)和大通道角模具(模具Ⅱ)以及A路径和Bc路径对单晶铜和多晶铜进行等通道角挤压(ECAP)实验,对挤压后的组织进行光学显微镜(OM)和扫描电镜(SEM)观察,对挤压后的单晶铜组织进行XRD分析,研究单晶铜和多晶铜在挤压中的变形行为。结果表明:单晶铜在两种路径挤压后的抗拉强度无明显差异,用模具Ⅰ挤压时其力学性能的变化幅度较大,经多道次挤压后,其显微组织沿压力轴方向具有明显的定向排列特征。多晶铜在A路径挤压时,其抗拉强度的上升幅度明显比在Bc路径挤压时大。随着挤压道次的增加,两种材料的组织均匀化程度和硬度增大,其断裂方式逐渐由韧性断裂向脆性断裂方向转变。

The mechanical properties of single crystal copper and polycrystalline copper were investigated by equal channel angular pressing （ECAP） through two die channels with small angles （DieⅠ） and larger angles （Die Ⅱ）, and on route A and route Bc. The microstructures of extruded samples were observed with optical microscopy（OM） and scanning electron microscopy（SEM）, and the microstructures of single crystal copper during extrusion were analyzed by X-ray diffractometry（XRD）. The deformation behaviors of single crystal copper and polycrystalline copper during extrusion were studied. The results show that the tensile strengths of single crystal copper extruded samples on route A increase faster than those on route Bc, and the difference between them first increases and then decreases. The mechanical properties of single crystal copper change quickly during extrusion with die Ⅰ. The microstructure of single crystal copper has obvious orientational characteristics along the forcing spindle after several extruding passes. During extrusion, the tensile strength of polycrystalline copper on route A increases more significantly than that on route Bc. With increasing the extrusion passes, the uniformity of the two kinds of materials improves and the hardness increases, and the mode of fracture changes gradually from ductile fracture to brittle fracture.