The significant size effect on nucleation and propagation of crack during tensile deformation of copper foil: Free surface roughening and crystallography study
The significant size effect on nucleation and propagation of crack during tensile deformation of copper foil: Free surface roughening and crystallography study
复制标题
铜箔拉伸变形过程中裂纹成核和扩展的显着尺寸效应：自由表面粗糙化和晶体学研究
DOI：
10.1016/j.msea.2020.139678
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发表时间：
2020-07-14
期刊：
影响因子：
6.4
通讯作者：
Misra, R. D. K.
中科院分区：
文献类型：
--
作者：
Chen, J. Q.;Gao, H. T.;Misra, R. D. K.
本文对80 μ m厚铜箔进行了拉伸试验，以阐明晶粒尺寸对裂纹形核和扩展的影响。实验结果表明，当试样厚度与晶粒尺寸之比（T/D）小于10时，晶粒尺寸越大，试样的断裂应力和应变越小。这是由于在拉伸变形的早期阶段的应变局部化。共聚焦激光扫描显微镜（CLSM）表明，在拉伸应变过程中，随着晶粒尺寸的增加，自由表面粗糙度增加。表面粗糙化引起的局部凹陷和试样减薄是裂纹扩展的前兆。对T/D值为1.8的试样进行了电子背散射衍射（EBSD）研究，观察到在裂纹尖端附近，存在高密度的致密且深的滑移痕迹。滑动过程逐渐由单次滑动到多次滑动再到交叉滑动。晶界和退火孪晶界都是位错运动的障碍，导致应变局部化。此外，在拉伸变形过程中，裂纹扩展方向并不总是垂直于加载方向。裂纹扩展方向的变化发生在晶界的交界处，并进入相邻的晶粒。大角度晶界对裂纹扩展提供了更大的阻力。
Tensile tests were conducted on copper foils with 80 mu m in thickness to elucidate the effect of grain size on nucleation and growth of crack. Experimental results indicated that samples with larger grain size had smaller fracture stress and strain when the ratio of sample thickness to grain size (T/D) was below 10. This is attributed to strain localization during the early stage of tensile deformation. Confocal laser scanning microscopy (CLSM) indicated an increase in free surface roughening with increase in grain size during tensile straining. The local depression trough and thinning of sample caused by surface roughening were precursors to crack propagation. (EBSD) studies of crack in sample with T/D value of 1.8, it was observed that in the vicinity of the crack tip, a high density of dense and deep slip traces were present. The slip process gradually changed from single slip to multiple slip and then to cross slip. Both grain boundary and annealed twin boundary acted as obstacles to the movement of dislocations and led to strain localization. Furthermore, during tensile deformation, the crack propagation direction was not always perpendicular to the loading direction. A change in the direction of crack propagation occurred at the junction of grain boundaries and entered into the adjacent grain. Large angle grain boundaries provided greater resistance to the propagation of crack.