Author:

Keywords:

Selective Laser Melting, Ti6Al4V, Residual Stress, Preheating, Microstructure, Oxygen

Abstract:

Selective Laser Melting of Ti6Al4V has already transitioned to commercial exploitation, but is still coping with two major limitations that restrict a more widespread use. Residual stresses can cause a premature build failure by inducing cracks in bigger parts, and deformations of fine features during the build and of the whole part after removal from the build platform. On the other hand, the ductility of the martensitic α’ microstructure is relatively low. Preheating of the build platform may provide a solution for both problems. It reduces thermal gradients and thus limits the development of residual stresses, but also causes a transformation of the α’ microstructure to a more ductile mixture of α+β. In this research, preheating of the base plate up to 400°C shows that residual stresses are reduced by 50%, and a transformation of the microstructure to a α+α’+β mixture. However, pickup of interstitial elements at elevated temperatures during the process leads to an embrittlement, reducing the ductility. Careful control of the atmospheric parameters may eliminate this issue, paving the way for build platform preheating to solve the current problems with SLM of Ti6Al4V.