The solidification behavior

hot cracking and microstructure of Al-7Zn-2.5Mg-Cu alloy were investigated with hot tear-linear contraction ZQS2000 twin bar tester for alloy

OM（optical microscope）

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 increased slowly during the solidification

and its shrinkage stress is generated and then increased dramatically with the dendrites formed a solid skeleton.The formation and propagation of the hot crack is located along the grain boundary of the α-Al 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 decrease of rate of the proeutectic volumetric shrinkage

the stronger ability of the liquid feeding as well as the less shrinkage of the eutectic.