In-Situ SEM Study on Deformation and Failure Mechanism of TC4 Titanium Alloy by Laser Additive Manufacturing

The in-situ tensile test of the field emission scanning electron microscope was used to study the deformation mechanism of the TC4 titanium alloy manufactured by laser additive manufacturing along the L direction (grain growth direction) and T direction (perpendicular to the grain growth direction). The test results show that during the tensile process, as deposited specimen mainly cracks along the interfaces of α and β which is 45 ° to the tensile direction. With the increase of load, the cracking increases. The surface of the sample fluctuates until breaks. There is no obvious change in the prior β grain boundary in L direction. The microcracks along grain boundaries were observed in T direction, which is consistent with the result that the plasticity in the T direction is less than that in L direction. After heat treatment, due to the increase of α lath width compared with the as-deposition, slip bands were observed in α phase. However, a large number of slip bands appear on the equiaxed α phase of the forged specimen.