Enhancing Strength and Ductility of a Ni-26.6Co-18.4Cr-4.1Mo-2.3Al-0.3Ti-5.4Nb Alloy via Nanosized Precipitations, Stacking Faults, and Nanotwins

Abstract

The addition of Co to Ni-based alloys can reduce the stacking fault energy. In this study, a novel Ni-26.6Co-18.4Cr-4.1Mo-2.3Al-0.3Ti-5.4Nb alloy was developed by increasing the Co addition to 26.6 wt.%. A new strategy to break the trade-off between strength and ductility is proposed by introducing dense nanosized precipitations, stacking faults, and nanoscale twins in the as-prepared alloys. The typical characteristics of the deformed alloy include dense dislocations tangles, nanotwins, stacking faults, and Lomer–Cottrell locks. In addition to the pinning effect of the bulky δ precipitates to the grain boundaries, the nanosized γ′ particles with a coherent interface with the matrix show significant precipitation strengthening. As a result, the alloy exhibits a superior combination of yield strength of 1093 MPa and ductility of 29%. At 700 °C, the alloy has a high yield strength of 833 MPa and an ultimate tensile strength of 1024 MPa, while retaining a ductility of 6.3%.

Keywords

• Ni-based alloy
• annealing time
• mechanical properties
• precipitation strengthening
• deformation mechanism