Controllable in-situ aging during selective laser melting: Stepwise precipitation of multiple strengthening phases in Inconel 718 alloy

A controllable in-situ aging treatment of Inconel 718 alloy was successfully developed by governing the types and times of the thermal cycles during selective laser melting (SLM). The sequential precipitation of gamma', composite phase of primary/secondary gamma' coated by a gamma '' shell, and gamma '' occurs as the times of vertical thermal cycles increase when laser peak temperature (T-P) is between the precipitation temperature of strengthening phase (T-pre) and liquid temperature (T-L). which causes an increase in microhardness by 40 HV. Also, short-term aging mechanisms on three types of strengthening phases are proposed based on a great number of vacancies in the matrix. (C) 2019 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.