N08811耐热合金的热变形行为与本构模型

Hot deformation behavior and constitutive model of N08811 heat-resistance alloy

采用Gleeble-3800热模拟试验机研究了N08811耐热合金在变形温度为900~1150℃、变形速率为0.1~5 s^(-1)条件下的高温变形行为。结果表明,N08811合金的流变应力随着应变速率的增大及变形温度的下降而增加,是一种正应变速率敏感材料。通过对显微组织的研究,发现当应变速率为1 s^(-1)时,N08811合金优先在变形晶粒的晶界处发生动态再结晶,再结晶晶粒数目及尺寸均随变形温度的升高而增加,至变形温度为1150℃时已发生完全再结晶。当变形温度一定时,高应变速率会降低N08811合金的再结晶温度,增加晶粒尺寸。依据真应力-真应变曲线,采用双曲正弦本构模型建立了N08811合金的流变应力本构方程,得到其热变形激活能为509.998 kJ·mol^(-1)。

The hot deformation behavior of N08811 heat-resistance alloy under the conditions of hot deformation temperature of 900-1150℃and strain rate of 0.1-5 s^(-1)was investigated by Gleeble-3800 thermal simulator.The results show that the flow stress of N08811 alloy increases with the increase of strain rate and the decrease of deformation temperature,and it is a positive strain rate-sensitive material.Through the observation of microstructures,it is found that when the strain rate is 1 s^(-1),dynamic recrystallization prefers to happen near the grain boundary of deformed grains,both the quantity and size of recrystallized grain increase with the increase of deformation temperature,and when the deformation temperature is 1150℃,fully recrystallization occurs.When the deformation temperature is fixed,high strain rate can lower the recrystallization temperature of N08811 alloy and increase the grain size.According to the true stress-true strain curves,the flow stress constitutive equation of N08811 alloy was established using the hyperbolic sinusoidal constitutive model,and its thermal deformation activation energy is 509.998 kJ·mol^(-1).