GH4710合金铸锭挤压后的动态再结晶行为及微观结构演变

Dynamic Recrystallization Behavior and Microstructure Evolution of As-extruded GH4710 Alloy Ingot

摘要:

研发了一种三联冶炼GH4710合金铸锭热挤压新工艺，以克服GH4710合金采用铸锻工艺变形难的问题。对挤压态GH4710合金进行了等温压缩实验和金相研究，分析了该合金在变形温度为1050～1120 ℃、应变速率为0.01～5.00 s^-1条件下的流变应力特征、动态再结晶（DRX）行为及微观组织演变。在不同的变形条件下，获得了真应力-真应变曲线、平均晶粒尺寸以及动态再结晶体积分数。采用统计回归方法，建立了挤压态GH4710合金的DRX体积分数和晶粒尺寸的预测模型。将模型写入Derform-3D软件中，并对该合金微观组织演化进行数值模拟。首先，通过有限元方法对等温压缩进行数值模拟，证实了模型的准确性。再者，将模型应用于直径为 300 mm的涡轮盘进行锻造工艺优化分析。结果表明：模拟所得的结果与采用最优工艺参数锻造的涡轮盘的实际微观结构之间存在很强的相关性。最优工艺参数为变形温度1100 ℃、锻造速度0.2 mm/s。这一DRX预测模型可作为GH4710合金铸锭挤压后热变形过程微观结构演变的基准参考。

Abstract:

A new triple melting method with hot extrusion process for GH4710 alloy ingots has been developed to overcome the difficulty in deformation of GH4710 alloy prepared by the casting and forging process. The as-extruded GH4710 alloy was analyzed through the isothermal compression experiment and metallographic analysis. The viscoelastic stress characteristics and dynamic recrystallization (DRX) behavior of the as-extruded GH4710 alloy were investigated during deformation at temperatures ranging from 1050 °C to 1120 °C and strain rates ranging from 0.01 s^-1 to 5.00 s^-1. The true stress-true strain curves, average grain size, and DRX volume fraction were also obtained under various deformation conditions. Prediction models for DRX volume fraction and grain size of the as-extruded GH4710 alloy were established using the statistical regression method. The model was implanted into the Derform-3D software, and numerical simulation of the microstructure evolution of GH4710 alloy was conducted. Firstly, the isothermal compression simulations were conducted using the finite element method to verify the accuracy of prediction model. Subsequently, the prediction model was applied to perform an optimization analysis of the forging process for a turbine disk with a diameter of 300 mm. Results show a strong correlation between the simulated results and the actual microstructure of the turbine disk forged through the optimal process parameters. The optimal process parameters are deformation temperature of 1100 °C and forging speed of 0.2 mm/s. This established DRX prediction model can serve as a fundamental reference for understanding the microstructural evolution during the hot deformation process of as-extruded GH4710 alloy.