TiC/Cu­Al2O3复合材料的强化机理及动态再结晶行为

摘要

The TiC/Cu­Al2O3 composite was prepared by vacuum­pressed and internal oxidation sintering. The microstructures were observed and the main strengthening mechanisms were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The hot deformation of the composite was investigated by the Gleeble-1500D thermal simulator. The tests were performed at the temperature of 450-850 ℃, the strain rate of 0.001-1 s-1 and the maximum strain of 0.7. According to the lnθ-εcurves and the-∂(lnθ)/∂ε-εcurves, the critical conditions of dynamic recrystallization and the volume fraction of dynamic recrystallization were obtained by the computation of the work hardening rate (θ) from initial true stress-true stain data. Based on the volume fraction of the dynamic recrystallization of the composite, the dynamic recrystallization kinetic equation was established. The results show that the strength of the composite is enhanced by the dispersion of theγ­Al2O3 particles and the amorphous layer between TiC and substrate. There exists the softening mechanism of dynamic recrystallization during the hot compression process. The volume fraction of dynamic recrystallization of the composite increases with the increase of the plastic strain and the deformation temperature, as well as the decrease of the strain rate.%采用真空热压-内氧化烧结法制备 TiC/Cu­Al2O3复合材料，通过扫描电镜(SEM)和高分辨率透射电镜(HRTEM)分析其微观组织，讨论该材料的强化机理。利用Gleeble-1500D热力模拟试验机在温度为450~850℃、应变速率为0.001~1 s-1及变形量0.7的条件下进行试验。采用加工硬化率处理法对真应力-真应变数据进行处理，结合lnθ-ε曲线和-∂(lnθ)/∂ε-ε曲线，确定该材料动态再结晶临界条件及动态再结晶体积分数，并利用该体积分数建立动态再结晶动力学模型。结果表明：内氧化生成γ­Al2O3颗粒的弥散强化作用及TiC与基体间的非晶过渡层提高了材料的强度；该复合材料热压缩过程中存在动态再结晶软化；随着变形量的增加、变形温度的升高及应变速率的降低，动态再结晶体积分数均增加。