Mechanical behavior of GH4720Li nickel-based alloy at intermediate temperature for different strain rates

Abstract

The GH4720Li alloy is one of the most widely used precipitation-strengthened nickel-based superalloy. However, systematic study about effect of strain rate on the plastic deformation behavior of GH4720Li alloy at intermediate temperature is lacking. The evolution of the tensile properties and plastic deformation mechanism of GH4720Li alloy with the strain rate at 650 °C were systematically studied with the help of transmission electron microscopy analysis. The results show that the tensile strength of the alloy increases and the plasticity decreases with the increase in strain rate. When the strain rate is 5 min⁻¹, the tensile strength of the alloy is 1448 MPa and the tensile plasticity is 18%. As the strain rate increases from 0.05 to 0.5 min⁻¹, the size and morphology of the primary γ′ phase of the alloy remain unchanged, with an average size of about 1.8 μm. However, when the strain rate further increases to 5 min⁻¹, the average size of the primary γ′ phase increases to 2.5 μm. In addition, the increase of strain rate has no significant effect on the size and distribution of secondary and tertiary γ′ phases. As the strain rate increases from 0.05 to 5 min⁻¹, the deformation mechanism of alloy gradually evolved from dislocation slip and twin to dislocation slip, indicating that the plastic deformation mechanism of the alloy presents a high strain rate sensitivity at 650 °C.