冷却速率对A357合金凝固组织的影响  

Effect of Cooling Rate on Microstructures of A357 Alloy During Solidification

作　　者：陈忠伟[1] 王晓颖[1] 张瑞杰[1] 介万奇[1] 

机构地区：[1]西北工业大学凝固技术国家重点实验室,陕西西安710072

出　　处：《铸造》2004年第3期183-186,共4页Foundry

基　　金：国家重点基础研究发展规划项目(G2000067202 1)。

摘　　要：以不同冷却速率铸造A357合金试样,用光学显微镜和扫描电镜(SEM)分析其凝固组织。通过不同冷却速率下的DTA试验研究了A357合金的凝固行为;采用DSC试验研究了不同冷却速率所得试样中相的变化;测定了这些试样的微观硬度。结果表明,随着冷却速率的提高,A357合金的宏观晶粒尺寸和二次枝晶臂间距减小,共晶Si相的形态更加细小,且分布愈加弥散;合金液相线温度和二元共晶的反应温度降低,三元或四元共晶反应被抑制,合金凝固组织中Mg2Si相的析出受到抑制,微观硬度明显提高。The A357 alloy was cast at different cooling rates. The microstructures of these samples were characterized with optical microscopy and scanning electron microscopy (SEM). The solidification beha-vior of A357 alloy was analyzed by the DTA at various cooling rates. DSC tests were carried out to determine the phases and their relative amounts in the as-cast samples. The micro-hardness of the samples were also measured. The results showed that the grain size and second dendrite arm spacing of A357 alloy were decreased and eutectic silicon phase was refined and dispersed by increasing the cooling rate. It also indicated that the liquidus temperature and the binary eutectic temperature were decreased and the ternary/quarternary eutectic reactions and Mg_2Si phase were restrained as the cooling rate increased. The micro-hardness of the sample at the higher cooling rate was distinctly raised.

关 键 词：A357合金 冷却速率 微观组织 凝固 

分 类 号：TG244.3[金属学及工艺—铸造]