Abstract: Strengthening metallic materials often compromises ductility primarily due to insufficient strain hardening capacity to sustain continuous plastic deformation. In this study, we introduce spinodal decomposition strengthening and bimodal grain structures into a Ni-based superalloy, achieving a remarkable synergy of strength and ductility. The alloy demonstrates a high yield strength of 1120 MPa, an ultimate tensile strength of 1548 MPa, and a uniform elongation of 26.2 %. Notably, this alloy undergoes a multi-stage strain hardening process: the spinodal structure initially enhances dislocation resistance and subsequently facilitates dislocation accumulation and interaction with stacking faults, extending plastic deformation. Our findings underscore the pivotal role of the spinodal decomposition structure in enabling multi-stage strain hardening, phenomenon rarely observed in Ni-based superalloys, offering valuable insights into the strain hardening mechanisms and offering a promising pathway for optimizing the performance of high-strength alloys through spinodal structures.

Key words: Spinodal decomposition structure, Heterogeneous grain, Multi-stage strain hardening, Strength and ductility