20Mo/Cu­Al2O3复合材料的强化机理及热变形行为

摘要

采用真空热压−内氧化烧结方法制备20%Mo/Cu­Al2O3复合材料，测试其性能并观察分析其微观组织。利用 Gleeble−1500D 热力模拟试验机在温度为350~750℃、应变速率为0.01~5 s−1及总应变量0.5的条件下，对20%Mo/Cu­Al2O3复合材料热变形过程中的流变应力与应变之间的关系进行研究。结果表明：20%Mo/Cu­Al2O3复合材料的组织分布均匀，未观察到明显的团聚现象及孔洞，致密度较高。在材料基体上，原位内氧化生成的纳米级Al2O3颗粒呈弥散分布，增加了基体的强度。复合材料的高温流动应力—应变曲线以动态再结晶软化机制为主，峰值应力随变形温度的降低或应变速率的升高而增加；在真应力—真应变曲线基础上建立的高温变形本构方程较好地表征了此复合材料的高温流变特性，其计算结果与实验结果吻合较好。%The 20%Mo/Cu­Al2O3 composites were prepared by vacuum­pressed in situ internal oxidation sintering, their properties and microstructures were tested and observed, respectively. Using the Gleeble−1500D thermal simulator, the relationship between the flow stress and strain during the hot deformation process of the 20%Mo/Cu­Al2O3 composites was investigated at temperature of 350−750 ℃, strain rate of 0.01−5 s−1 and total strain of 0.5. The results show that the microstructures of the 20%Mo/Cu­Al2O3 composites well distribute, no aggregate phenomena and holes are observed, and the density is relatively high. The in situ internal oxidation generated nano Al2O3 particles distribute dispersively, which enhances the body strength of the composites. The softening mechanism of dynamic recrystallization of the composites is a feature for the high­temperature flow stress—strain curves of the composite, and the peak stress increases with the decrease of deformation temperature or the increase of strain rate. Based on the true stress—true strain curves, the established constitutive equation represents the high­temperature flow behavior of the composite, and the calculated results of the flow stress are in good agreement with the experimental results of the high­temperature deformation.