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采用激光熔注技术在Ti-6Al-4V表面制备了单晶颗粒增强的WCp/Ti-6Al-4V梯度复合材料层。利用扫描电镜原位拉伸试验,观察复合材料层裂纹形成、扩展的动态过程,研究其微观断裂行为。结果表明,WCp/Ti-6Al-4V复合材料层的失效机制主要有两种:WC颗粒开裂和WCp/Ti界面开裂。WC颗粒开裂是主要失效形式,WCp/Ti界面开裂的比例相对较少,而且主要发生在较高的应变情况下。激光熔注条件下形成的规则胞状反应层有利于应力由基体传向增强颗粒。在拉伸过程中,WC颗粒内部应力由最初的压应力逐渐变为拉应力。WC颗粒内部拉应力的极大值可达2000MPa,高于单晶WC陶瓷的抗拉强度。
The single crystal grain reinforced WCp / Ti-6Al-4V gradient composite layer was prepared on the surface of Ti-6Al-4V by laser melting technology. In-situ tensile test by scanning electron microscopy (SEM) was used to observe the dynamic process of crack formation and propagation in the composite layer and to study the microscopic fracture behavior. The results show that there are two main failure mechanisms of WCp / Ti-6Al-4V composites: WC particles cracking and WCp / Ti interface cracking. WC particles cracking is the main failure mode, WCp / Ti interface cracking is relatively small, but mainly in the case of higher strain. The regular cell-like reaction layer formed under laser melting conditions facilitates the transfer of stress from the substrate to the reinforcing particles. During the stretching process, the internal stress of WC particles gradually changes from initial compressive stress to tensile stress. The maximum tensile stress of WC particles can reach 2000MPa, which is higher than the tensile strength of single-crystal WC ceramic.