Tensile properties and deformation mechanisms of two low-cost second-generation single crystal superalloys designed by optimization of Re and W compositions at various temperatures

Abstract

In this work, two novel low-cost second-generation single crystal superalloys were designed by optimizing compositions of W and Re elements. The tensile properties and deformation mechanisms were systematically investigated from room temperature to 1070 ℃. It was found that yield strength of both alloys reached the maximum value (1099 MPa for 1.0Re alloy and 1086 MPa for 1.5Re alloy) at 760 ℃. At room temperature and 760 ℃, dislocations sheared into γ′ phase and dissociated into partial dislocations and stacking faults, which controlled the whole deformation process. At 760 ℃, the interactions between isolated stacking faults caused by the successive initiation of multiple slip systems led to the formation of Lomer-Cottrell locks, which effectively improved yield strength of 1.0Re alloy. 1.5Re alloy was strengthened effectively by isolated stacking faults, Kear-Wilsdorf locks and dislocation loops at 760 ℃. At high temperatures (980 ℃ and 1070 ℃), dislocation pairs with anti-phase boundary shearing into γ′ phase became the main deformation mechanism, and dislocations climbing and bypassing mechanisms could also be activated under higher thermal activation. Meanwhile, compared with that in 1.0Re alloy, interfacial dislocation networks in 1.5Re alloy is more regular and denser. Generally, the two novel self-designed single crystal superalloys characterized by outstanding tensile properties and cost reduction displayed great potentials for application of advanced aero-engines in the future.