Al_2O_3/Cu复合材料的高温变形行为

High temperature deformation behavior of Al_2O_3/Cu composites

采用Gleeble-1500热模拟试验机和透射电子显微镜研究了变形温度为300~900℃,应变速率为0.01~10s-1条件下Al_2O_3/Cu复合材料的高温流变行为和组织演变规律,并利用Arrhenius关系和Zener-Hollomn参数构建了合金的峰值屈服应力、变形温度和应变速率三者之间的本构方程。结果表明:Al_2O_3/Cu复合材料的流变应力-应变曲线为典型的动态再结晶类型,其曲线由加工硬化、动态软化和稳定流变3个阶段组成,当变形温度一定时,流变应力随应变速率的增大而增大,而当应变速率固定时,流变应力随变形温度的升高而减小;求解得到复合材料的结构因子lnA为15.2391,应力水平参数a为0.020788mm^2/N,应力指数n为5.933035,变形激活能Q为2.1697×10~5kJ/mol;随着变形温度的升高,基体内位错密度逐渐下降,并呈现出明显的再结晶特征,而当固定变形温度时,随着应变速率的增大,基体内位错密度呈先增大后下降趋势。基于微观组织演变和热加工图,Al_2O_3/Cu复合材料的最佳热加工参数范围为热加工温度500~850℃、应变速率低于0.1s-1。

The flow behavior and microstructure evolution of Al_2O_3/Cu composites,which conducted at deformation temperature of 300-900℃and strain rate of 0.01-10s-1,were investigated by using Gleeble-1500 thermal simulator and TEM analysis.A constitutive equation of the peak value yield stress-deformation temperature-strain stress was also defined based on the Zener-Hollomn parameter and Arrhenius equation.The results show that the stressstrain curve of the composites is a typical softening mechanism of dynamic recrystallization type,and the curve consists of work hardening,dynamic softening and stabilization stage.The peak value of stress decreases with the increase of deformation temperature or the decrease of strain rate.In addition,the material parameters of the composites are obtained as follows：the structure factor lnAof 15.2391,the stress level parameterαof 0.020788mm^2/N,the stress exponent nof 5.933035,and the deformation activation energy Qof 2.1697×10~5 kJ/mol.With increasing of deformation temperature,the dislocation density in the matrix is gradually decreased,and an obviously recrystallization feature appears.However,in the case of isothermal compression,the dislocation density is increased at first,and then decreased,with increasing of strain rates.According to the microstructure evolution and hot processing maps,the optimum processing condition for good hot workability of Al_2O_3/Cu composites can be summed up as：temperature range 500-850℃ and strain rate range below 0.1s-1.