Microstructure, precipitates and mechanical properties of Inconel 718 alloy produced by two-stage cold rolling method

Abstract

In order to improve the mechanical properties of Inconel 718 alloy, two-stage cold rolling method was applied, which involved primary cold rolling, intermediate annealing, secondary cold rolling and aging treatment. A large number of short rod-shaped and spherical δ particles precipitated on grain boundaries, which could effectively improve the plasticity of Inconel 718 alloy. Subsequent secondary cold rolling and two-stage aging treatment improved the strength of the material through the combined effects of work hardening and precipitation of γ'' + γ′ strengthening phases. The aged samples after secondary cold rolling exhibited an excellent combination of yield strength (~ 945 MPa), ultimate tensile strength (~ 1080 MPa), and total elongation (~ 36%) when deformed at 650 °C. And its ultimate tensile strength at room temperature is ~ 1500 MPa. These excellent mechanical properties can be attributed to the proper fraction of δ phase precipitates, together with optimal morphology of δ phase.