Effect of Powder Properties and Heat Treatment on Microstructure Evolution of Selective Laser Melted Titanium Alloy

Titanium alloy powder with different particle size distribution was obtained by powder screening and mixing. The effects of physical properties of powders on the quality and deposited- and heat-treated-microstructure of selective laser melted (SLM) titanium alloy component were studied. The results show that with the increase in the proportion of fine powder, powder median size decreases, fluidity decreases while the bulk density does not change significantly; the relative density of parts from the powder with three kinds of particle sizes is more than 99%; the surface roughness decreases with the increase of fine powder content; when the quantity of fine powder is 23%, the minimum porosity forms after deposition; the as-deposited microstructure of the cross section is primary beta grain, the internal is acicular martensite, and the longitudinal section is the visible columnar crystal; heat treatment results show that martensite decomposes to alpha+beta layer at 600 similar to 800 degrees C, and the alpha+beta layer becomes thicker at 800 degrees C. The annealing temperature and time during the heat treatment process should be strictly controlled to avoid layer coarsening.