在Gleeble-1500热模拟试验机上进行多组热压缩试验,得到7075铝合金在成形温度573～723K,应变速率0.01～10s-1下的真应力-应变数据,用此数据作为计算应变速率敏感指数（m值）、功率耗散因子（η值）、失稳判据（ξ（ε.）值）三重判据的基本模型。通过三重判据构建包含应变在内的7075铝合金热加工图,并观察试样变形后的微观组织来验证热加工图,最终判断该合金在试验范围内的最佳变形参数。结果表明7075铝合金热加工的安全区集中在高温低应变速率区,并随着应变的增加,η值逐渐增加;通过金相观察,稳定变形区,材料由于变形发生动态再结晶而使晶粒细化;不稳定变形区,裂纹伴随着流动位错带的产生而被发现,因此可以通过包含应变的热加工图所确定的最佳工艺参数来保证无缺陷的7075铝合金锻件。
The hot deformation behaviors of 7075 aluminum alloy at the temperature range of 573-723K and strain rate range of 0.01-10s-1 have been studied by using hot compressing testing on a Gleeble-1500 simulation,then the true stress-strain data collected resulted the performance of calculations for strain rate sensitivity（m-value）,power dissipation efficiency（η-value） and instability parameter（ξ-value） under the different ture strain.The processing maps including strain of hot deformation of 7075 aluminum alloy was constructed according to three criterion of the above,and the microstructures of deformed specimens were observed as a evidence index.The regions of flow instabilities and optimum hot working condition are can be attained from the processing map and microstructure.The results show that the security domain mainly of hot working for 7075 aluminum alloy in the high temperature and low strain rate region,furthermore the power dissipation factor increase gradually with increasing strain;by the metallographic observations,the grain refinement by dynamic recrystallization under the stable deformation conditions,and bands of flow localization which have been associated with cracking under the unstable deformation conditions.The optimal working parameters identified by the processing maps including strain contribute to designing the hot forming process of 7075 aluminum alloy forging without any defect.
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