Microstructure and anisotropic tensile behavior of laser additive manufactured TC21 titanium alloy

In the present work, two types of part with different geometries were fabricated by laser additive manufacturing (LAM) process under the same processing parameters. Tensile samples perpendicular to (horizontal) and parallel to (vertical) the build direction were produced after heat treated under different conditions. The results showed that the samples exhibit similar columnar β grains, but very different α phase characterizations. The tensile properties show significant anisotropic. The sample containing finest α laths shows highest ultimate tensile strength and yield strength. And the strength decreased with the increase of α laths width. The total elongation of the samples does not show regularity relationship with the strength. The horizontal samples show inferior ductility and brittle fracture due to the columnar β grain morphology and the presence of continuous grain boundary α layers. The coarse grain boundary α layers after double heat treatment further reduced the ductility. The vertical samples exhibit better ductility due to lack of continuous grain boundary α layers which perpendicular to the tensile load. The Vickers hardness test shows that the vertical samples were strengthened while the horizontal samples were little strengthened after tensile test.