中应变率下纯铜强迫剪切行为的研究

Forced shear behavior of pure copper under medium strain rate

沿退火纯铜板材法向取帽型试样,用万能试验机在中应变率(1 s^-1)下对其进行压缩试验。借助金相显微、电子背散射衍射(EBSD)技术、显微硬度测试等手段,研究不同变形纯铜强迫剪切变形行为特征。结果表明:在中应变率下,试样力学响应加工硬化明显。变形主要集中在帽形试样两端的豁口连接处,且出现裂纹,并形成两端向中部扩展趋势。随变形量增加,剪切区域内部的晶粒首先沿剪切方向被拉长,随后破碎成等轴细晶,小角度晶界占比率逐步降低,越靠近剪切带,硬度越高,带内硬度明显高于带外。剪切带内晶体择优取向明显,且不同变形量样品的织构特征类似。

The hat-shaped samples were cutted from the annealed pure copper sheet along normal direction.The compressive performance was tested under the condition of medium strain rate(1 s^-1)by means of universal testing machine.Optical microscopy(OM),micro-hardness test and electron backscatter diffraction(EBSD)were used to investigate the forced shear behavior under different deformation degree.The results show that the flow stress shows obvious work hardening effect under medium strain rate.The deformation is mainly concentrated at the gap junction of two sections of hat-shaped samples,and cracks appear in the shear region.The two ends of the shear band extend to the middle.With the increase of deformation,the grains in the shear band are elongated and refined into equiaxed grains with the proportion of low angle grain boundary decreases.The closer to the shear band,the higher the micro-hardness.The micro-hardness in the band is significantly higher than that outside the band.Strong texture is formed inside the shear band of each sample,and the texture characteristics of samples with different deformation are similar.