Fracture Behavior of Heat Affected Zone of Laser-welded Joint for Ti-6Al-4V titanium alloy: Experimental and Computational Study

In order to study failure perspective of Ti-6Al-4V titanium alloy welded joint, fracture behavior of the heat affected zone is researched. Microhardness, tensile test and microstructure are used to study the mechanical properties of the titanium alloy laser welded joint. The tensile and microhardness results show that heat affected zone near the base metal is the weakest in welded joints. This paper is based on the results from in-situ tension test to observe the process of crack expansion in heat affected zone. And then, in-situ test is simulated via the finite element method on ABAQUS Standard; therefore the fracture criteria are generated by comparing the applied force between simulation and in-situ test. Meanwhile, the GTN model is used to describe the damage behavior of the titanium alloy. The grain structure is simplified as voronoi convex polyhedron. And then, based on the in-situ test and its simulation, we conduct research on the fracture driving force under micro-scale condition. The simulation result indicates that the driving forces for metal fracture are jointly from the normal stress and shear stress.