Haynes242高温合金热加工图及再结晶行为研究

Hot Processing Map and Recrystallization Behavior of Haynes242 Superalloy

目的Haynes242高温合金由于弹性模量几近恒定,膨胀系数低,被广泛应用于生产航空发动机高温密封环件。但是,由于Haynes242合金中Cr、Ni、Mo合金元素含量高,使得其热加工成型性对工艺参数极度敏感。因此,探索其最优热加工工艺参数,以期提高该合金热加工成型件的质量。方法采用Gleeble热模拟试验机研究Haynes242合金在950~1100℃温度范围内和0.001~1 s^(-1)的应变速率条件下的热变形行为。随后,通过光学显微镜分析各变形条件下Haynes242合金的微观组织演变规律。结果通过对Haynes242合金能量耗散图和失稳图的绘制,获得了该合金在不同变形量下的热加工图。通过分析Haynes242高温合金的热加工图及显微组织的演变规律,发现该合金材料的再结晶行为对变形速率和变形温度非常敏感。高温、低应变速率时发生动态再结晶程度最大,材料的可加工性更好。结果显示,Haynes242高温合金的最佳热变形工艺参数为1050~1100℃/0.001 s^(-1)。结论基于Poliak和Jonas提出的临界再结晶模型,确定了Haynes242合金的临界再结晶应变模型。此外,还揭示了变形温度和变形速率对动态再结晶行为的影响机制。

Haynes242 superalloy is widely used in producing high temperature sealing rings due to its near constant elastic modulus and low coefficient of expansion.The work aims to explore the optimal hot working processing parameters of Haynes242 alloy to improve the hot working forming quality of the alloy,because the alloy has high content of Cr,Ni and Mo and is very sensitive to hot working processing parameters.Gleeble thermal simulation test machine was used to test the thermal deformation behavior of the Haynes242 alloy at the deformation temperature of 950-1100℃and the strain rate of 0.001-1 s^(-1).The microstructure evolution of Haynes242 alloy under different deformation conditions was analyzed with an optical microscope.The hot processing map of the Haynes242 superalloy under different deformation was obtained by drawing the energy dissipation and the instability criterion diagrams.According to the hot working map and the microstructure analysis of the Haynes242 superalloy,it was found that the recrystallization behavior of the alloy material was very sensitive to the deformation rate and temperature.The highest degree of dynamic recrystallization occurred at high temperature and low strain rate.At this time,the machinability of the material was better.The results showed that the optimum thermal deformation parameters of the Haynes242 superalloy were 1050-1100℃and 0.001 s^(-1).Furthermore,the critical recrystallization strain model of Haynes242 alloy is determined based on the critical recrystallization stain model proposed by Poliak and Jonas,and the effects of deformation temperature and strain rate on dynamic recrystallization behavior are revealed.