低温等通道转角挤压中定向凝固纯铜的组织及性能演变

摘要

采用光学显微镜(OM)和XRD技术对干冰冷却后的定向凝固纯铜(99.99％)经等通道转角挤压(ECAP)时的微观组织演变规律进行研究,并测试了ECAP后定向凝固纯铜的硬度及导电性能.结果表明,定向凝固纯铜在低温下经A和C路径变形后易于形成取向一致的纤维组织,并且保持(111)面的择优取向特征,而经Bc路径变形后,柱状晶破碎,形成均匀的等轴晶,且各晶面逐渐趋于随机取向;经过1道次变形后,各路径硬度大幅增加,约为原来的1.8倍,在随后的挤压中,硬度增加缓慢,经4道次ECAP后,Bc路径的硬度有所下降;在低应变下,晶粒取向的一致性使得导电率增加;随着应变的增加,晶格畸变使得电子发生散射,使导电率略有降低.%The microstructure evolution of directional solidification structure in pure copper (99 .99％)during equal channel angular pressing (ECAP)after cooling with dry ice was investigated by OM and XRD,the hardness and conductivity were tested. The results manifested that the fibrous structure with same orientation was formed in directional solidification structure in pure cop-per by route A and C at low temperature,and the characterization of (111 )preferred orientation was remained.After deformation by route Bc,columnar crystal of directional solidification structure in pure copper was broken,and homogeneous equiaxed grains were formed,at the same time,the grain orientation tended to be random.The hardness of each route increased drastically after one pass extrusion,which was about 1 .8 times in compare with hardness of original sample,with the increase of extrusion passes,the hard-ness increased slowly,whereas the hardness decreased slightly after four passes extrusion by route Bc.The consistency of grain orientation made the conductivity increased in the condition of low strain,however,with the increase of strain,lattice distortion caused electron scattering,which leaded to a slight decrease in conductivity.