The effect of hydrogen treatment on microstructures evolution and mechanical properties of titanium alloy fabricated by selective laser melting

The selective laser melting additive manufacturing can realize near-net forming and produce complex high-precision parts. However, β-columnar crystals will be formed in building direction, which leads to the decrease of material reliability, causing stress concentration and accelerating material fracture. Here, we perform hydrogenation treatment, solution treatment, aging treatment, and finally dehydrogenation treatment on Ti-6Al-4V titanium alloy fabricated by selective laser melting. The results show that the β grains of hydrogenated samples are refined after subsequent heat treatment. After the solution treatment, α' and α'' martensite coexist in the microstructure and decomposed during the subsequent aging and dehydrogenation treatment, resulting in the refinement of the structure within the grains, but still retaining the grain morphology of the previous alloy. When compressed at room temperature，the compressive strain and ultimate compressive strength of hydrogenated samples after heat treatment increase with the increase of hydrogen concentration, and the yield strength decreases. After dehydrogenation, the yield strength and ultimate compressive strength are increase.