SiC_P/Al-Cu复合材料动态再结晶行为及临界条件

利用Gleeble-1500D热模拟试验机对40%SiC_P/Al-Cu复合材料进行压缩实验,研究其在温度为350~500℃、应变速率为0.01~10 s~(-1)条件下的高温塑性变形行为。由实验得出变形过程中的应力-应变曲线,采用加工硬化率处理方法对应力-应变数据进行处理,结合lnθ-ε曲线的拐点和(-α(lnθ)/αε)-ε曲线最小值的判据,研究该复合材料动态再结晶临界条件。结果表明:40%SiC_P/Al-Cu复合材料的应力-应变曲线主要以动态再结晶软化机制为特征,峰值应力(σ_p)随变形温度的降低或应变速率的升高而增加;该材料的lnθ-ε曲线出现拐点,(-α(lnθ)/αε)-ε曲线出现最小值;临界应变(ε_c)随变形温度的升高与应变速率的降低而减小,且临界应变与峰值应变(εp)之间具有相关性,即ε_c=0.528εp;临界应变与Zener-Hollomon参数(Z)之间的函数关系为ε_c=4.58×10~(-3)Z~(0.09)。透射电镜观察显示应变为0.06时(变形温度为400℃,应变速率为10 s~(-1))已经发生动态再结晶,应变为0.2时,动态再结晶晶粒充分长大。

Dynamic Recrystallization Behavior and Critical Conditions ofSiCp/A1-Cu Composite

Using the Gleeble-1500D simulator, the high temperature plastic deformation behavior of 40%SiCP/Al-Cu composite were investigated at 350-500 ℃ with the strain rate of 0.01-10 s-1.The stress-strain curves were obtained during the tests.The critical conditions of dynamic recrystallization for onset of DRX during deformation of 40%SiCP/Al-Cu composite was obtained by computation of the strain hardening rate (θ) from initial stress-strain data and introduction of the inflection point criterion of ln θ-ε curves and the minimum value criterion of (-(e)(ln θ)/(e)ε)-ε) curves.The results indicate that the softening mechanism of the dynamic recrystallization is a feature of high-temperature flow stress strain curves of the composites, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate.The inflection point in the ln θ-ε curve appears, and the minimum value of the (-(e)(ln θ)/(e)ε)-ε) curve is presented when the critical state is attained for this composite.The critical strain decreases with the decrease of strain rate and the increase of deformation temperature.There is linear relationship between critical strain and peak strain, i.e.εc=0.528εp.The predicting model of critical strain is described by the function of εc=4.58×10-3Z 0.09.Electron microscopic analysis show that the dynamic recrystallization occurs when the strain is 0.06 (T=400 ℃, (ε)=10 s-1), and the dynamic recrystallization grains fully grow up when the strain is 0.2.