GH5188合金板材高温拉伸变形流动行为与本构方程研究

目的 研究GH5188合金板材高温拉伸变形流动行为，为高温合金板材高温成形工艺的制定和优化提供指导。方法 基于GH5188合金板材高温拉伸试验，分析了变形工艺参数对GH5188合金板材高温拉伸变形时真应力、应变速率敏感性指数和应变硬化指数的影响规律，建立了本构模型对其流动行为进行描述和预测。结果 GH5188合金板材高温拉伸变形流动行为受应变硬化、流动软化和应变速率硬化的共同影响，其变形过程分为弹性变形、加工硬化、稳态流动和断裂4个阶段。随变形温度的升高和应变速率的降低，真应力减小。变形温度、应变速率和真应变对GH5188合金板材的应变速率敏感性指数和应变硬化指数具有显著影响。基于Johnson-Cook和Hensel-Spittel模型，建立了考虑应变硬化效应、流动软化效应和应变速率硬化效应耦合影响的GH5188合金板材高温拉伸变形本构模型(JC-HS模型)，采用该模型预测的真应力与试验值的平均相对误差为6.02%。结论 建立的JC-HS模型能够较好地描述和预测GH5188合金板材的高温拉伸流动行为。

Flow Behavior and Constitutive Model of GH5188 Superalloy Sheet during Hot Tensile Deformation

The work aims to understand the flow behavior of GH5188 superalloy sheet during hot tensile deformation to provide guidance for formulation and optimization of its hot forming process. Based on the hot tensile experiments of GH5188 superalloy sheet, the influence of process parameters on the true stress, strain rate sensitivity index and strain hardening index of GH5188 superalloy sheet was studied. A constitutive model was established to describe and predict its flow behavior. The results showed that the flow behavior of GH5188 superalloy sheet was determined by strain hardening, thermal softening and strain rate hardening. The hot tensile deformation process could be divided into four stages:elastic deformation, work hardening, steady flow and fracture. With the increase of deformation temperature and the decrease of strain rate, the true stress decreased. The deformation temperature, strain rate and true strain had significant effects on the strain rate sensitivity index and strain hardening index of GH5188 superalloy sheet. Based on Johnson-Cook and Hensel-Spittel models, a hot tensile deformation constitutive model (JC-HS model) of GH5188 superalloy sheet was established considering the coupling effect of strain hardening, thermal softening and strain rate hardening. The average relative error between the true stress predicted by this model and the experimental value was 6.02%. In conclusion, the JC-HS model can well describe and predict the hot tensile flow behavior of GH5188 superalloy sheet.