Comparison study of microstructure and mechanical properties of standard and direct-aging heat treated superalloy Inconel 706

The present study reports a detailed investigation of the microstructure and mechanical properties of superalloy Inconel 706 which was heat treated using standard and direct-aging schemes. The results indicated that the direct-aging heat treatment led to 11.2% increase in yield strength, 6.1% increase in ultimate tensile strength and 80% increase in 650 °C/690 MPa stress rupture life for the alloy compared to that was heat treated using the standard heat treatment scheme. The mechanisms associated with the improvement in mechanical properties were discussed based on the microstructure characterizations. The superior strength for the direct-aged alloy was attributed to its smaller grain size, finer η precipitates, and finer γ″ particles. The results indicate that direct-aging is an effective heat treatment which can improve the mechanical properties of alloy Inconel 706, and it has the potential to be applied in some special environments.