High strength and ductility in a novel Ni-based superalloy with γ′ and nanotwins / stacking faults architectures

Abstract

The variation of microstructure, which depends on the processing history, significantly affects the mechanical properties of alloys. Here, thermo-mechanical treatments were employed to control the microstructure and tune the corresponding mechanical properties of a Ni-based superalloy. The nanotwins can be successfully introduced into the superalloy after cold rolling reduction amount of 70%. Meanwhile, the nanotwins are thermally stable during subsequent annealing at 950 °C for 2 h and two-step aging processes (650 °C/24 h/AC and 760 °C/16 h/AC). The high yield strength of 1691 MPa has been obtained in the partially recrystallized structure. The high strength originates from the dislocations and deformation nanotwins induced by cold rolling, and γ′ particles. When compared to the initial condition, the yield strength and elongation of the fully recrystallized structure are simultaneously increased from 1043 MPa to 19.5% to 1386 MPa and 20.5%, respectively. The strength-ductility combination is derived from the fine-grains, annealing twins and γ′ particles coupled with a high density of intersected SFs with LC locks. In addition, the unique work hardening behavior is mainly related to the intersected SFs and LC locks configuration. The present study provides a strategy to obtain the desirable mechanical properties of Ni-based superalloy via proper thermo-mechanical treatments.