Effect of the δ Phase on the Tensile Properties of a Nickel-Based Superalloy

Abstract

Nickel-based superalloys are widely used in aerospace and other fields due to their excellent properties. In this study, the aging treatment and tensile tests of a GH4169 alloy were carried out. The effects of the δ phase on the alloy’s mechanical properties and fracture behavior were studied. The results showed that the appearance of the δ phase changed from a short rod shape to a needle shape with an increase in aging time. The precipitation method changed from a single mode of precipitation along the grain boundary to two modes of precipitation along the grain boundary and direct precipitation inside the grain. The yield strength and ultimate tensile strength of the alloy first increased and then decreased with an increase in aging time and were related with the microstructure of the δ phase. The similar Widmanstatten structure was not conducive to the mechanical properties of the alloy. The distribution of the δ phase led to the generation of inhomogeneous strain and limited the surface roughening during plastic deformation. The voids initiated at the interface between the δ phase and the matrix γ phase or directly from the δ phase fracture site.

Keywords

• superalloy
• microstructure evolution
• tensile deformation
• strain evolution
• fracture