Anisotropic response of Ti-6Al-4V alloy fabricated by 3D printing selective laser melting

The 3D printed bulk samples fabricated by selective laser melting (SLM) of the additive manufacturing technique are usually considered to be 3D isotropic in microstructures and mechanical responses. This study systematically investigates the anisotropic responses in terms of hardness and electrochemical resistance for the X-, Y- and Z-planes of the SLM Ti-6Al-4V bulk samples fabricated with the zigzag laser path strategy. Results show that all SLM planes exhibit no significant difference in Young's modulus compared to the mechanically rolled plate. However, the X-plane, referred to the cross-sectional plane perpendicular to the laser moving direction, is found ~20% lower hardness and the lowest corrosion resistance compared to the Y- and Z-planes. The underlying reasoning is researched and discussed. The microstructure observations indicate that artifact holes are induced in the X-plane due to un-uniform laser intensity distribution between two neighboring printing lines. Alternatively, the Y- and Z-planes exhibit dense morphology due to multiple heating while zigzag scanning. Experimental results also indicate that the SLM materials exhibit higher corrosion resistance than the commercial rolled materials.