Microstructure and mechanical properties of laser powder bed-fused IN625 alloy

Abstract This study focuses on linking the mechanical properties of laser powder bed fusion-processed IN625 alloy, more specifically its propensity for elevated temperature ductility loss, to the microstructure of this alloy resulted from different post-processing heat treatments. Firstly, it is shown that delta phase precipitates formed during stress relief annealing at 870 °C are not responsible for the elevated temperature ductility loss, since their dissolution after intermediate-temperature annealing at 980 °C did not allow improving the alloy ductility. Secondly, it is shown that carbide precipitates contained in the solution-treated alloy (1120 °C) are not responsible for this ductility loss either, since increasing their content during subsequent aging of the solution-treated alloy did not significantly affect the alloy ductility at elevated temperature. Finally, it is demonstrated that deformation of the solution-treated alloy at elevated temperatures is accompanied by dynamic strain aging, while deformation of the stress-relieved and intermediate temperature-annealed specimens is accompanied by dynamic recrystallization. Thus, it seems that at elevated temperatures, there is competition between the dynamic strain aging and dynamic recrystallization processes, with the former decreasing, and the latter increasing the alloy ductility.