Effect of building direction on microstructure and mechanical properties of SLM TC4 alloy

In the selective laser melting (SLM) technology, the microstructure and mechanical properties of the sample were affected by the building direction. In this paper, the effects of building direction on the microstructure and mechanical properties of SLM TC4 alloy were investigated of using optical microscope, scanning electron microscope, microhardness tester and MTS-Landmar material testing machine. The results show that the microstructure of SLM TC4 alloy consists of acicular martensitic α′ phase. The microstructure of SLM TC4 alloy in the horizontal build direction (H) was observed to have “checkerboard” shape, while the microstructure of SLM TC4 alloy in the vertical build direction (V) was observed to have column shape. The microhardness of SLM TC4 alloy with different building directions are almost the same and the tensile properties are different. The yield and tensile strengths of sample H are higher at 995.5 MPa and 1139.3 MPa, but the fracture elongation of sample V is better at 10.3%. The fracture mechanism of SLM TC4 alloy is ductile fracture and the V sample has large and deep dimples.