合金在冷却过程中的收缩行为对于热成形零件的尺寸精度和性能有着重要的影响.采用透射电镜、X射线衍射、热模拟实验相结合的分析方法,研究了不同冷却速率条件下7A09铝合金的冷却收缩行为.结果表明：在冷却过程中,该合金的主要相转变是η相（MgZn2）析出.η相的析出降低了合金体系的结合能,引发了合金热收缩系数相应的非线性变化.当冷却速率增大时,η相的析出量随之减少,热收缩系数则随着η相析出量的减少而增大.
Alloy cooling contraction behavior has an important effect on accuracy and properties of hot processed parts.In this work,thermal simulation experiments were carried out,and with transmission electron microscopy and X-ray diffraction,the cooling contraction behavior of 7A09 aluminum alloy at different cooling rates was investigated.The results indicate that the precipitation of η phase（MgZn2） is the predominant transformation in 7A09 alloy during the cooling process.The precipitation of η phase decreases cohesive energy of alloy and consequently causes the corresponding nonlinear change of thermal contraction coefficient（TCC）.The amount of η phase decreases with the increasing of cooling rate,and TCC increases as the amount of η phase decreases.
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