Laves相NbCr2/Nb两相合金的热变形行为及基于响应面法的变形工艺参数优化

Hot deformation behavior of Laves phase NbCr2/Nb two-phase alloy and optimization of deformation process parameters based on response surface method

摘要:

Laves相NbCr2/Nb两相合金因具有作为高温结构材料应用的潜力而引起了较广泛的研究关注。基于合金在1273-1473K和0.001-0.1s-1^{条件下的等温}恒应变速率压缩实验数据,分析了Laves相NbCr2/Nb两相合金的流变应力行为,计算了热变形激活能Q、功率耗散效率η和失稳因子 ；建立了以变形工艺参数为输入变量,Q、η和 为响应目标的响应面模型,并基于多目标优化获得了适宜的变形工艺参数窗口条件。结果表明,Laves相NbCr2/Nb两相合金为正应变速率和负温度敏感材料；在所研究的工艺参数范围,Q、η和 值分别在157.0~659.3 J/mol,0.01~0.81和-0.6229~0.6359范围波动,这说明合金的塑性变形能力对工艺参数变化敏感；所建立的Q、η和 响应面模型具有较高的预测精度,其决定系数R2^分别达到0.992,0.999和0.953,平均绝对相对误差AARE分别为1.29%,0.63%和11.5%；变形工艺参数对Q的交互影响顺序(从大到小)为：变形温度/应变速率＞应变速率/真应变＞变形温度/真应变,而变形工艺参数对η和 的交互影响顺序基本相同,即,变形温度/应变速率＞变形温度/真应变＞应变速率/真应变；基于低Q,高η和 的多目标优化而获得的适宜变形工艺窗口条件为1440-1473K和0.001-0.05s-1^{,最佳变形工艺}条件在1473K、0.001s-1^{附近。对最佳变形工艺条件下的微观组织验证表明,基于多目标优化获得的变形工艺}窗口条件是正确的。

Abstract:

Laves phase NbCr2/Nb two-phase alloy has attracted extensive research attention due to its potential as high temperature structural materials. Based on the isothermal constant strain rate compression experimental data of the alloy at temperatures ranging from 1273 to 1473 K and strain rates ranging from 0.001 to 0.1 s^-1, the flow stress behavior of the alloy was analyzed, the thermal deformation activation energy Q, power dissipation efficiency η and instability factor were calculated, response surface models with the deformation process parameters as input variables and Q, η and as response targets was established, and the appropriate window conditions of deformation process parameters were obtained by multi-objective optimization. The results show that Laves phase NbCr2/Nb two-phase alloy is a positive strain rate and negative temperature-sensitive material. The values of Q, η and values fluctuate within the range of 157.0-659.3 J/mol, 0.01-0.81 and -0.6229-0.6359, respectively, which indicates that the plastic deformation capacity of the alloy is sensitive to the change of process parameters. The established response surface models for Q, η and have high prediction accuracy with the determination coefficients R² reaching 0.992, 0.999 and 0.953, respectively, and the average absolute relative errors AARE are 1.29%, 0.63% and 11.5%, respectively. The interaction order of deformation process parameters on Q (from large to small) is as follows: deformation temperature/strain rate>strain rate/true strain>deformation temperature/true strain, while the interaction order of deformation process parameters on η and is basically the same, that is, deformation temperature/strain rate>deformation temperature/true strain>strain rate/true strain. Based on the multi-objective optimization of low Q, high η and , the appropriate deformation process window conditions are 1440-1473K and 0.001-0.05s^-1, and the optimal deformation process window condition is around 1473K and 0.001s-¹. Microstructural verification under the optimal deformation process conditions confirms the correctness of the deformation process window conditions obtained through multi-objective optimization.