摘要
研究了稀土（0.1%～1.2%,质量分数）对Mg-Al合金抗热裂性能的影响及其机制.结果表明： 往Mg-Al合金中添加稀土后,合金的抗热裂性能显著下降,其原因可归为： 稀土引起了Mg-Al合金晶粒粗化,使得热裂纹萌生所需的断裂应变降低;稀土减少了Mg-Al合金中的共晶组织,缩短了枝晶通道保持开通的时间,不利于合金进行补缩;而且稀土还提高了共晶反应的温度,使得凝固后期枝晶间液膜的强度有所下降;当α-Mg枝晶连成骨架时,分布在枝晶间的Al11RE3相容易堵塞枝晶通道,增加了合金补缩的难度;Al11RE3相与α-Mg基体的凝固收缩率不同,容易产生凝固收缩应力,促进热裂纹的萌生.
The effect and mechanism of rare earth on the hot cracking resistance of Mg-Al alloys were investigated. The results show that the hot tearing resistance of Mg-Al alloys remarkably declines with the increasing amount of rare earth addition. The causes of the decline in the hot tearing resistant property are as follows： The grain coarsening of Mg-Al alloys by rare earth decreases the fracture strain required by initiation of the hot tears. RE reduces the amount of the eutectic microstructure of Mg-Al alloys, shortens the time which keeps the feeding channel open and makes the alloy difficult to feed. Furthermore, rare earth elevates the eutectic reaction temperature, which leads to the decrease of the strength of the interdendritic liquid film at the late stage of solidification. When the α-Mg dendrites form the continuous skeletons, the interdendritic Al11RE3 phases tend to block the feeding channels and increase the difficulty of feeding. Since the shrinkage ratios between Al11RE3 phases and α-Mg matrix are quite different, it is prone to cause the shrinkage stress and promote the initiation of hot tears.
出处
《中国稀土学报》
CAS
CSCD
北大核心
2006年第2期205-210,共6页
Journal of the Chinese Society of Rare Earths
基金
北京市科技计划项目(Y0405004040211)资助
关键词
镁-铝合金
热裂
稀土
Mg-Al alloys
hot tearing
rare earths
