中文摘要：

在微塑性成形试验机上对纯铜圆柱试样进行恒定速度的微镦粗试验。通过热处理和精细线切割技术,设计不同的试样尺寸和晶粒尺寸。分别研究晶粒尺寸和试样尺寸对微塑性成形的影响。研究发现：试样流动应力随着试样尺寸的减小而减小,其减小趋势与表面晶粒体积分数存在线性关系;当试样尺寸较大时,晶粒尺寸对试样流动应力的影响并不明显,而随着试样尺寸的减小,大尺寸晶粒试样的流动应力要明显低于小晶粒尺寸的试样;当试样尺寸较小时,试样在微镦粗过程中表现出明显的不均匀性。通过表面层理论和细晶强化对有试样尺寸和晶粒尺寸变化引起的尺寸效应现象进行解释,同时,引入尺度参数量化由试样尺寸引起的尺寸效应现象,从而对当应变一定时流动应力随着表面层晶粒体积分数φ呈现近似线性变化的原因进行解释。

英文摘要：

The process of pure copper micro-cylinder upsetting is performed by a micro universal testing machine. Through the heat treatment and precision wire cutting technology, the specimens are designed with different dimensions and grain sizes. The effects of grain size and specimen size on the flow stress are investigated, respectively. It is found that the flow stress decreases with the miniaturization of the specimen size and the relationship between flow stress and volume fraction of surface grain is linear. The effect of grain size on the flow stress is indistinct as the specimen is larger, but the flow stress of the specimen with larger grain size is obviously lower than that with small size. The surface of the micro-forged specimens show significant inhomogeneous deformation as the specimen size is smaller. The size effects due to the changing of specimen size and grain size can be explained by surface model and fine grain strengthening theories. Meanwhile, the scale parameter is introduced to quantify the size effect and thus the linearly changing of follow stress with the volume fraction ~ can be explained.