Temperature dependence on tensile deformation mechanisms in a novel Nickel-based single crystal superalloy

Abstract

The affordability has become a key element in the development of the modern aero-engines thus the design and research of low-cost single crystal superalloys are in great demand. A kind of novel Nickel-based single crystal superalloy with cost reduction was designed in this work and the temperature dependence on the microstructure modification as well as corresponding deformation mechanisms during tensile tests were systematically investigated. The experimental alloy exhibited a remarkable yield strength of 912 MPa but relatively poor ductility at 760 °C. At higher temperatures, an overt strain softening occurred before the tensile rupture and the fracture features were identified as dimples induced by the accumulated micro-pores. The stacking faults shearing mechanism prevailed at room temperature and there presented two types of stacking faults in the γ′ precipitates. Both decomposition and cross-slip of the a/2 <101> superdislocation were observed at 760 °C while the deformation mechanism was controlled by APB-coupled dislocation pairs shearing the γ′ phase at 980 °C. With temperature increasing to 1100 °C and 1120 °C, the amount of shearing dislocation pairs decreased dramatically, besides, the interfacial dislocation networks and rafted γ/γ′ structures were formed. The degradation of mechanical properties was considerably slight from 1100 °C to 1120 °C, however, three primary microstructure modifications were emphasized.