Effect of Heat Treatment on Hardness and Microstructure of Titanium Alloy (Ti6Al4V) via Laser Powder Bed Fusion (LPBF)

Laser powder bed fusion (LPBF) is one of additive manufacturing (AM) processes which emits high power lasers on powder coatings to produce 3D end products. The combination of main processing parameters such as laser power, velocity scanning, hatching distance and layer thickness resulted to volumetric energy density (VED) which influence the performance of 3D products. For metals, residual stresses are often caused by repeated fusion and solidification of molten metal on each printed layer which may reduce the performance of 3D end products if not eliminated. Heat treatment is often employed to overcome such issue. In this work, the effect of heat treatment on the hardness and microstructure of titanium alloy (Ti6Al4V) printed via the LPBF process was investigated. It was found that at high VED, the hardness was reduced by 20% from 417.35HV (untreated) to 333.37HV (heat-treated). Microstructure analysis shows that phase changes from α (untreated) to α + β phase after the heat treatment. Such combination of phases improves the product’s stiffness. The findings from this study can be applied to other Ti6Al4V products such as automotive and medical implants where suitable performance is achievable.