工业纯铜极薄带轧件的微尺度效应

Micro-scale effect of CP-copper ultrathin strip

利用自主研发的微型异步轧机,制备出工业纯铜极薄带材。通过拉伸试验、微观硬度测试、显微组织观察和XRD检测研究了极薄带的机械性能随厚度的变化规律。结果表明,极薄带抗拉强度和硬度值随样品厚度减小,呈现出先增大后减小的规律,即出现微尺度效应,且其位错密度值亦出现先增大后减小的规律。原始晶粒在经过深度塑性变形后,前期的位错塞积导致加工硬化,当极薄带的厚度小于某极限值后,由于比表面积增加,剧烈塑性变形形成的位错容易移动至晶界处消失,此时位错的削减速率大于增殖速率,材料发生软化。

An independently developed micro asymmetrical mill was applied to produce ultra-thin strip of CP-copper （commercially purecopper）. Tensile and micro hardness test were carried out on roiled CP-eopper foil with different thickness to study the mechanical propertieschanging rule with thickness, it was founded that the ultimate tensile strength and micro hardness increased t^rst and lhen decreased withdecreasing thickness, ealled micro-scale effect. The dislocation density was calculated based on XRD （X-ray diffraction） results. The resultsshow that the dislocation density increases first, then decreases with the thickness of uhrathin strips decreases. After deep plasticdeformation, the early dislocation pile-up causes the strain-hardening in the original grains. When the thickness of the exlremcly thitl beh issmaller than certain limit value, because the specific surface area increases, the dislocations formed by the intense plastic detormationdisappear by moving to the grain boundary. At this time the dislocation reduction rate is greater than the multiplication rate, the the CP-copper softens.