Dependence of microstructure and mechanical properties on heat treat cycles of electron beam melted Ti-6Al-4V

The EBM Ti-6Al-4V alloy has generally superior mechanical properties, owing to finely spaced α−β laths which give a good combination of strength and ductility. The grain structures in the as-printed structures are long columnar which can give rise to anisotropic mechanical properties. Moreover the non-uniformity in microstructure can also arise from part geometry where the thin features have propensity to form martensite phase. Heat treatment provides a viable solution to modify the microstructure and to tailor to the properties as desired. A wide range of heat treatment experiments were performed, followed by microstructure and tensile property analyses. It was observed that the microstructure and the tensile properties significantly changed depending on the heat treat cycle performed. Tensile properties of solution treated air-cool plus aged samples yielded globular equiaxed grains with fine α−β lath structure, which were found to be the best among the different heat treated samples and better than ASTM F1472 specifications.