(中南大学 粉末冶金研究院，长沙 410083)
摘 要: 通过Gleeble-3180热模拟机对具有细晶组织的镍基粉末高温合金U720Li进行高温热压缩变形实验，分析该合金在1000~1150 ℃、0.001~1 s-1应变速率的变形条件下的流变行为。利用采集的应力-应变数据计算材料的热变形激活能，构建材料的本构方程，建立合金的热加工图，并通过微观组织观察对热加工图进行解释。结果表明：失稳区主要位于低温高应变速率区域，合金未发生明显动态再结晶现象，晶界处的应力集中导致沿晶裂纹的产生。在1150 ℃、0.01 s-1条件下，晶粒明显长大；在1100 ℃、0.001 s-1条件下，变形能够获得细小均匀的晶粒组织。
关键字: 镍基粉末高温合金；本构方程；热加工图；微观组织
（Research Institute of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:Hot deformation on a fine-grained P/M superalloy U720Li was performed at 1000-1150 ℃ and strain rate of 0.001-1 s-1 by the Gleeble-3180 simulator. The deformation activity energy and constitutive equations were established by the true stress and true strain data. Processing maps for hot working were established on the basis of the variations of power dissipation efficiency, and related them with the microstructure observation. The results show that the major instability domain locates at low temperature and the high strain rate region, which is mainly caused by intergranular cracks, and the dynamic recrystallization doesn’t occurred. The grain growth is remarkably triggered under 1150 ℃, 0.01 s-1. Optimum hot working condition for U720Li is determined as 1100 ℃ and 0.001 s-1, where the refined and uniform grains are observed.
Key words: nickel-based powder superalloy; constitutive model; hot processing map; microstructure
