单向拉伸与压缩时粗晶纯锌的形变及损伤行为

Deformation and damage behavior of coarse-grained pure zinc under unidirectional tension and compression

对具有密排六方(hcp)结构的粗晶纯锌(纯度为99.995%)试样进行单向拉伸与压缩实验,研究其形变及损伤行为。用金相显微镜和扫描电镜对试样的表面变形形貌以及断口形貌进行观察。结果表明:单向拉伸试样塑性很差,只有当应变速率很小时才表现出一定的塑性,在形变过程中几乎没有滑移系开动,只有少量孪晶产生,断口主要以解理断裂为主;单向压缩试样的塑性远优于相同应变速率下的拉伸试样,不同压缩量试样的形变与损伤方式略有不同,主要有孪生(包括二次孪晶)、滑移和裂纹的形成等;晶界在不同载荷下也有不同的表现。

The deformation and damage behavior of coarse-grained pure zinc （purity of 99.995%）, with typical hcp structure, were investigated under unidirectional tension and compression. The surface deformation features and fracture surfaces of all deformed samples were observed by optical microscopy and scanning electron microscopy. The results show that under unidirectional tensile deformation, this material exhibits a very poor plasticity. Only under the case that the strain rate is very low, does the pure zinc show somewhat of plasticity. The slip systems can hardly operate under this circumstance, and only a few deformation twins can be found. Cleavage fracture is the major mode of a final failure of samples. In contrast, the samples of pure Zn present much better plasticity under compressive tests than under tensile tests at comparable strain rates. The deformation and damage behavior are slightly distinctive under different compressive strains, consisting of twinning （including formation of secondary twins）, slip deformation, cracking, etc. Grain boundaries act as varying roles under different loading conditions.