Fine grains within narrow temperature range by tuning strain-induced boundary migration dominated recrystallization for selective laser melted Inconel 718

Abstract

In this study, fine grains are achieved with weak texture of selective laser melted Inconel 718 (SLM IN718) if annealed within a narrow temperature range (1,070 ∼ 1,090 °C), while abnormal grain growth (AGG) is induced if annealed at temperature higher than that range, resulting in large matrix grains and twins. By a novel quasi-in-situ electron backscatter diffraction (EBSD) method, the recrystallization of SLM IN718 is primarily dominated by strain-induced boundary migration (SIBM) at 1,150 or 1,075 °C via statistical analysis. In particular, AGG at 1,150 °C is attributed to quick consumption of the high-strain regions due to a higher grain boundary (GB) velocity, while fine grains at 1,075 °C attributed to activation of more SIBM grains and uniform growth of these grains due to a slower GB velocity. The techniques proposed in this study can also work well for other SLM face-centered cubic alloys.