Achieving Exceptional Strength-Ductility Synergy in René 104scy Superalloyfabricated by Laser Powder Bed Fusion Through Induced Heterogeneous Microstructures

Abstract

Balancing strength and ductility present a significant challenge in the heat treatment of γ′ phase-strengthened nickel-based superalloys. This study successfully introduced multi-scale heterogeneous microstructures through direct heat treatment for the first time, achieving the excellent strength-ductility synergistic effect of LPBFed René 104ScY superalloy. The formation mechanism of the heterogeneous microstructure during heat treatment and its correlation with mechanical properties are discussed in detail. The results demonstrate that heat treatment led to the formation of a multi-scale heterogeneous microstructure, comprising bimodal grains, dispersed γ' phases, and nanotwins formed during recrystallization. These microstructures activated various strengthening mechanisms, significantly enhancing strength. Tensile stress induces stacking faults, Lomer-Cottrell locks, and 80-nanometer secondary twins, activating multiple plastic deformation modes. This enhances work-hardening capacity while preserving good ductility. The heat treatment process designed in this study achieved a good match between strength (yield strength: 1281±8 MPa, tensile strength: 1609±7 MPa) and elongation (16.6±0.3%). These findings propose a novel strategy for designing and developing precipitation-strengthened superalloys.

Keywords: Heterogeneous microstructure, Laser powder bed fusion, Twins, Stacking faults, Strength-ductility synergy