(1. 中南大学 粉末冶金国家重点实验室,长沙 410083;
2. 中南大学 航空航天学院,长沙 410083)
摘 要: 通过热模拟试验,系统研究热挤压-退火态FGH96合金在变形温度为1020~1110 ℃、应变速率为0.001~1 s-1条件下的热压缩变形行为,建立本构方程并构建热加工图;结合电子背散射衍射(EBSD)分析,优化合金的变形工艺参数。结果表明:合金在热变形过程中发生明显动态再结晶现象。利用摩擦修正后的峰值应力获得的该合金热压缩本构方程材料常数分别为:α=0.0071272、n=2.6417、A=6.6811×1015、Q=448.05 kJ/mol,较低的变形激活能与热挤压后初始晶粒尺寸的减小以及二次γ′相的粗化有关。利用构建的不同应变量ε下热压缩本构方程材料常数的五次多项式组对合金的流变应力进行了预测,预测数据与实验摩擦修正数据吻合较好。根据热加工图能量耗散效率并结合微观组织分析,对热挤压-退火态FGH96合金提出了建议的热加工参数范围:变形温度约为1075~1080 ℃、应变速率约为1×10-3~1×10-1.5 s-1的区域。
关键字: FGH96合金;热压缩变形;本构方程;变形激活能;热加工图
(1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China)
Abstract:Hot compressive deformation behavior of as hot extruded-annealed FGH96 alloy was systematically investigated at the temperatures from 1020 ℃ to 1110 ℃ with strain rates from 1×10-3 to 1 s-1 by thermal simulation experiments. The constitutive equation for hot compression of the alloy was established, and the hot processing map was also constructed. Combined with electron backscatter diffraction (EBSD) analysis, the deformation parameters of the alloy were optimized. The results show that apparent dynamic recrystallization occurs during hot deformation of the alloy. By using the friction-corrected peak stress data, the material constants of the constitutive equation for hot compression of the alloy are obtained to be α=0.0071272, n=2.6417, A=6.6811×1015, Q=448.05 kJ/mol, respectively. The lower activation energy of deformation is closely related to the decrease of initial grain size after hot extrusion and the coarsening of secondary γ′ precipitate. A group of five-order polynomials showing the relationship between material constants of the constitutive equation and strain is built up, by which the flow stresses are predicted. The predicted data are in good agreement with the experimental friction-corrected one. Considering the energy dissipation efficiency in the hot processing map and the microstructural analysis, the hot working parameters of the as hot extruded-annealed FGH96 alloy are suggested to be the deformation temperatures of about 1075-1080 ℃ and the strain rate of about 1×10-3-1×10-1.5 s-1.
Key words: FGH96 alloy; hot compression deformation; constitutive equation; deformation activation energy; hot processing map