材料期刊网

本文通过静态拉伸试验机和高应变速率冲击拉伸试验装置,对AZ91D压铸镁合金分别进行了不同应交率下(10~(-4)、10~(-2)、300和1 400 s~(-1))拉伸力学性能的试验,获得了各应变速率下完整的应力-应变曲线.并通过扫描电镜对其拉伸断口进行分析.试验结果表明,其屈服应力(σ_s)、拉伸强度(σ_b)随着应变速率的增加而增加,失稳应变(ε_b)则随着应变速率的增加而有所减小;而弹性模量则对应变率不敏感.采用John-son-Cook材料模型描述AZ91D镁合金应变速率相关的应力应变本构模型,其拟合结果和实验结果基本相吻合.扫描电镜断口分析结果表明,动态和静态的断裂方式基本相同,都是以准解理断裂特征为主,局部区域伴有解理断裂;存在典型的缩松断裂形貌.

Tensile experiments of casting Mg-alloy AZ91 D under different strain-rate (10~(-4)、10~(-2)、300 and 1400s~(-10) were carried out by static tensile testing machine and tensile impact testing apparatus and then the complete stress-strain curves were obtained. Fractures were also analyzed through stereoscan. The results showed that the yield strength σ_s, the uhimate strength σ_b and the failure strain ε_b varied slightly with the strain rate increase under low strain-rate or high strain-rate; Compared static state with dynamic state, the strain-rate influenced the material mechanical properties to some extent; while the modulus E was not insensitive to the strain-rate. To describe the stress-strain constitutive modle coherent with strain ratio of Mg-Alloy AZ91D with Johnson-Cook matial modle, and the fitted results is according with the experimental results. SEM fractographic analysis indicated that the mode for static and dynamic fracture were more or less the same, the material frac-ture was a mixed mode of predominant quasi-cleavage fracture and minor cleavage fracture, typical feature of shrinkage porosity fracture were presented as well.