Therefore, there is an obvious diff

Therefore, there is an obvious difference in temperature field between the melted part and the unmelted part in the forming process, resulting in a large temperature gradient in the forming process, and at the same time, residual stress is easy to occur in the rapid cooling process. In the process of selective melting, the metal is squeezed by the unmelted part due to the thermal expansion effect of the melted part, resulting in a compressive stress. When the melting zone is cooled, there is a cold shrinkage effect, which is subjected to the tensile stress of the surrounding powder