Melting and solidification behavior of Ti-6Al-4V powder during selective laser melting

To investigate melting and solidification behavior during selective laser melting (SLM), the shape of the solidified materials and energy balance during SLM were evaluated through temperature measurements with a two-color pyrometer. The laser power and scanning speed were selected as parameters to melt Ti-6Al-4V powder in a square area. The input energy per unit area used during SLM was 5, 10, 16, or 20 J/mm². The melting depth and width increased as the input energy increased. However, the aspect ratio of the melted area was constant. The mass ratio of melted to sintered material decreased as input energy increased. It was considered that the surplus input energy was used for sintering when the energy was high. Color maps show that the surface temperature distribution around the laser irradiation area was asymmetric, in which the temperature gradient at the solidified material side was smoother than that at powder side. The temperature history showed that melting and solidification occurred repeatedly during irradiation.