单晶颗粒增强WC_p/Ti-6Al-4V梯度复合材料层微观断裂行为

Micro Fracture Behavior of Single Crystal Particle Reinforced WC_p/Ti-6Al-4V Functionally Graded Materials Layer

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。

Laser melt injection（LMI） was used to prepare single crystal particle reinforced WCp/Ti-6Al-4V functionally graded materials（FGMs） layer on Ti-6Al-4V.In situ tensile test in scanning electron microscope（SEM） was employed to study the crack formation and propagation of the FGMs layer.The micro fracture behavior was also studied.The results show that there are mainly two failure mechanisms：WC particle cracking and WCp/Ti interface decohesion.WC particle cracking forms the majority of the crack nucleation.In contrast,WCp/Ti interface decohesion is a rarely observed phenomenon,which usually occurs at higher strains.In addition,the regular cellular reaction layer formed in LMI plays a positive role in the load transfer from the matrix to the particle.During the tensile test,the stress state of WCp gradually changes from initial compressive stress to tensile stress.Furthermore,the maximum tensile stress inside the WC particle is about 2000 MPa,which is much higher than the critical fracture strength of single crystal WCp.