Enhanced strength-ductility synergy of laser powder bed fused Inconel 718 via tailoring grain structure and precipitates

Abstract

Inconel 718 fabricated by laser-powder bed fusion (L-PBF) exhibits a hierarchical microstructure, rendering traditional standard heat treatment processes not entirely suitable. To enhance the tensile properties, a novel heat treatment strategy to simultaneously tailor the grain structure and precipitates of L-PBFed Inconel 718 is proposed. This study aims to investigate the effects of homogenization time, coupled with water cooling, on grain structure, precipitation, and room-temperature tensile properties. The results demonstrate that increasing the homogenization time from 1 h to 4 h results in a significant improvement of tensile ductility by 33.7%, while maintaining higher tensile strength compared to the wrought counterparts. The utilization of water cooling following homogenization effectively suppresses the formation of undesirable δ phases and promotes the precipitation of γ′′ phases during subsequent aging treatment, leading to exceptional tensile strength. Furthermore, the prolonged homogenization time facilitates recrystallization and promotes uniform deformation between adjacent grains, thereby enhancing the material's ductility. This study provides theoretical guidance for the development of customized heat treatment processes to achieve superior mechanical properties in additive-manufactured metallic materials.