Sr变质对ZL101合金显微组织和低温拉伸性能的影响

摘要

In this paper,the effect of modification treatment on the morphology of Si phase and tensile crack initiation and extension in the process of stretching of ZL101 alloy was studied,by means of analyzing the mechanical properties of ZL101 alloy at 20 ℃ and-60 ℃ stretching temperature.Microstructures of ZL101 alloy were analyzed by means of optical micro-scope(OM) and scanning electron microscopy(SEM).The results show that Si phase morphology can be improved and the split action of rigid Si to the aluminum can be reduced by modification of Sr,so that the mechanical properties of ZL101 alloy was improved.Tensile strength of ZL 101 alloy at-60 ℃ was higher than at 20 ℃,and elongation is opposite.In the process of low temperature tensile of ZL101 alloy,dislocation and Si phase with different size,distribution and morphology interact,most of the micro-cracks formed in the form of Si phase fracture.The crack extension rate of ZL101 alloy at low temperature is lower than that at room temperature,and tensile strength at low temperature is higher than that at room temperature.%通过对ZL101合金在20℃和-60℃拉伸温度下的力学性能进行分析,利用光学显微镜、扫描电镜对合金显微组织进行观察,研究变质处理对ZL101合金显微组织中Si相形貌和低温拉伸过程中裂纹的萌生与扩展的影响.结果表明:Sr变质处理可以改善合金中Si相形貌,降低硬质Si相对铝基体的割裂作用,从而ZL101合金力学性能得到提高.ZL101合金在-60℃温度下的抗拉强度高于20℃的,伸长率则相反.对于ZL101合金,在低温拉伸过程中,位错与不同尺寸、分布及形貌的Si相发生交互作用,大部分以Si相断裂的方式形成微裂纹,低温下裂纹扩展速率低于室温,从而使ZL101合金的抗拉强度低温高于室温.