Laves相NbCr2/Nb两相合金高温流动应力行为及本构关系建立

Thermal deformation behavior and constitutive relationship ofLaves phase NbCr2/Nb dual-phase alloy

摘要:

采用Gleeble-3500型热模拟试验机对机械合金化+热压工艺制备的Laves相NbCr₂/Nb两相合金进行等温恒应变速率压缩试验,研究合金在800~1200℃,0.001~0.1s^_-1条件下的流动应力行为,并分别基于双曲正弦函数型Arrhenius方程和逐步回归法建立合金的本构关系。结果表明,Laves相NbCr₂/Nb两相合金的韧脆转变温度大约在950~1000℃之间。当温度≤950℃时,合金尚未达到屈服就已发生断裂；当温度≥1000℃时,合金呈现出较好的塑性变形能力。合金流动应力随变形温度增加和应变速率降低而降低。合金在1050~1200℃、0.001s^_-1和1150~1200℃、0.01s^_-1条件下呈现流动稳态型特征；在1000℃、0.001s^_-1,1000~1100℃、0.01s^_-1和1000~1200℃、0.1s^_-1条件下呈现流动软化型特征。基于双曲正弦函数型Arrhenius方程建立的峰值流动应力本构关系和应变补偿本构关系的平均绝对相对误差AARE分别为9.89％和13.859%；基于逐步回归法建立的全实验条件下的本构关系、流动应力稳态型曲线本构关系和流动应力软化型曲线本构关系的平均绝对相对误差AARE分别为8.63%、5.28%和6.83%。所建立的几种本构关系,可为Laves相NbCr₂/Nb两相合金的锻造工艺制定、锻造设备吨位选择以及锻造过程有限元数值模拟提供理论依据和基础数据。

Abstract:

The isothermal constant strain rate compression test of the Laves phase NbCr₂/Nb dual-phase alloy prepared by mechanical alloying and hot pressing was investigated in the temperature range of 800~1200℃ and the strain rate range of 0.001~0.1s^_-1 by a Gleeble3500 thermal simulation tester. The flow stress behavior and the constitutive relations based on the hyperbolic sinusoidal function Arrhenius equation and the stepwise regression method were studied. The results show that the ductile to brittleness transition temperature (DBTT) of Laves NbCr₂/Nb dual-phase alloy is about 950~1000℃. The alloy breaks into pieces directly without yield below 950℃. While, it shows good plastic deformation ability above 1000℃. The flow stress of the alloy decreases with the increase of deformation temperature and the decrease of strain rate. It is characterized by steady-state flow under the deformation conditions of 1050~1200℃/0.001s^_-1 and 1150~1200℃/0.01s^_-1. While, it shows the flow softening under the deformation conditions of 1000℃/0.001s^_-1, 1000~1100℃/0.01s^_-1 and 1000~1200℃/0.1s^_-1. The AARE of the peak flow stress constitutive relation and the strain-compensated constitutive relation, which are established based on hyperbolic sinusoidal function Arrhenius equation, is 9.89% and 13.859%, respectively. The AARE of the constitutive relation under all experimental conditions, the steady-state flow stress curve constitutive relation and the softening flow stress curve constitutive relation, which are established based on stepwise regression method, is 8.63%, 5.28% and 6.83%, respectively. The established constitutive relation can provide theoretical guidance and basic data for forging process design, forging equipment tonnage selection and forging process finite element numerical simulation of the Laves phase NbCr₂/Nb dual-phase alloy.