不同工艺条件下A356合金的力学性能、微观组织和热疲劳特性研究  

Microstructure,Mechanical Properties and Thermal Fatigue Behavior of A356 Alloy Under Different Technological Conditions

作　　者：丁冉[1] 司乃潮[1] 刘光磊[1] 王宏健[1] 王正军[1] 

机构地区：[1]江苏大学材料科学与工程学院,江苏镇江212013

出　　处：《铸造》2016年第1期6-12,共7页Foundry

基　　金：江苏省科技厅科技型企业技术创新资金项目(BC2012211);江苏大学高级人才科研启动基金(14JDG126);江苏大学研究生科研创新计划项目(KYXX_0001);江苏大学第13批科研立项资助(13A457)

摘　　要：研究了不同工艺条件下A356微观组织、力学性能和热疲劳特性。结果表明:细化变质+微合金化+T6工艺的A356合金力学性能、热疲劳性能最优。热疲劳裂纹萌生期为沿晶生长,扩展期为沿晶+穿晶混合生长。裂纹扩展速率呈先增加后减缓的趋势,未脱落的Al_2Cu相、裂纹分叉与二次裂纹的产生均会减缓裂纹扩展速率。循环初期形成的氧化膜可抵消部分拉应力,阻碍氧化腐蚀;后期氧化膜遭到破坏,氧化腐蚀加剧,裂纹扩展加速。裂纹生长过程:位错滑移→空位→微坑→微裂纹→尖端闭合、张开→扩展。The microstructure, mechanical properties and thermal fatigue properties of A356 treated by different process conditions were studied. The results show that the thermal fatigue properties and mechanical properties of sample with compound refinement modification ＋ micro-alloying ＋ T6 heat treatment are optimal. Fatigue crack expanded along the grain boundary in initiation period. During expanding period, fatigue crack expanded with both intergranular way and transgranular way. The crack propagation rate showed a trend of increasing first then decreasing. Not peeling A12Cu phase, crack bifurcation and secondary cracks were the cause of the crack growth rate slowing. The formation of the oxide film in the early thermal fatigue experiment can offset part of the tensile stress, and therefore, prevented oxidation corrosion. In the late stage, the oxide film was destroyed, so that oxidation corrosion intensified and the crack propagation accelerated. The process of thermal fatigue crack initiation and propagation： micro dislocation glide→vacancy→pit→microcrack→tip closed and opened→extension.

关 键 词：A356合金 热疲劳 氧化 萌生 扩展行径 

分 类 号：TG146.21[一般工业技术—材料科学与工程]