The thermal cycling curves of ZAlSi7Cu4 treated by different heat treatment were drawn on a self-restrict thermal fatigue experimental machine at 25～350 ℃ to understand the effect of different heat treatment processes on the thermal fatigue behavior of the alloy.The thermal fatigue mechanism was analyzed by observing thermal fatigue crack morphology of the alloy samples with the help of OM（optical microscope） and SEM（scanning electron microscope）.The results show that the sample with T6 heat treatment is superior to one treated by other process in thermal fatigue resistance at 350 ℃.The expansion path of the crack can be controlled by the location of the grain

and the crack generation in the edge of the cavern can be slowed down with a higher curvature radius.The micro-hardness of the sample surface is decreased with the increase of the thermal cycle number

however

the microhardness of the samples treated by T6 and as-cast quenching plus aging has a slightly ascension in the period before the initiation of the crack.