Al-7Zn-2.5Mg-Cu合金的热裂机理  

Hot Cracking Mechanism of Al-7Zn-2.5Mg-Cu Alloys

作　　者：黄胜[1] 陈淑婉[1] 陈晓[2] 

机构地区：[1]运城学院机电工程系 [2]福州大学机械工程及自动化学院

出　　处：《特种铸造及有色合金》2013年第8期703-706,共4页Special Casting & Nonferrous Alloys

摘　　要：采用ZQS2000型双试棒合金热裂线收缩仪、金相显微镜、扫描电镜以及能谱分析等研究了Al-7Zn-2.5Mg-Cu合金的凝固特性与热裂。结果表明,该合金凝固过程中,冷却速率与线收缩率先快后慢。收缩应力在固相网形成后产生,并急剧上升。该合金的热裂纹在α-Al基体相的晶界上形成并发展。其热裂取决于共晶转变前初晶的收缩应变率、液相的补缩和共晶转变过程中共晶体积的收缩。共晶转变前初晶的收缩应变率小、液相补缩及时,共晶转变过程中共晶数量较少,其体积收缩小,都会减小合金的热裂倾向。The solidification behavior, hot cracking and microstructure of A1-7Zn-2.5Mg-Cu alloy were investigated with hot tear-linear contraction ZQS2000 twin bar tester for alloy, OM （optical micro- scope）, SEM （scanning electron microscope） and EDS（energy dispersive spectrometer）. The results show that the cooling rate and linear shrinkage of the alloy are rapidly increased firstly and then in- creased slowly during the solidification, and its shrinkage stress is generated and then increased dramat- ically with the dendrites formed a solid skeleton. The formation and propagation of the hot crack is loca- ted along the grain boundary of the a -A1 matrix phase, which is depended on the rate of the proeutectic volumetric shrinkage and the ability of the liquid feeding before the eutectic reaction, and the eutectic shrinkage in the eutectic reaction process. The hot cracking tendency of the alloy is decreased with de- crease of rate of the proeutectic volumetric shrinkage, the stronger ability of the liquid feeding as well as the less shrinkage of the eutectic.

关 键 词：AL-ZN-MG-CU合金 凝固 热裂 机理 

分 类 号：TG146.21[一般工业技术—材料科学与工程]