Microstructure evolution and creep behavior of Inconel 718 alloy subjected rolling process

Abstract

The Inconel 718 alloy is extensively utilized in aerospace applications due to its exceptional creep resistance. The impact of the rolling process on the evolution of the microstructure and creep properties of the alloy necessitates a thorough investigation. In this study, a comprehensive analysis was conducted to compare the microstructure, creep behavior, and damage mechanisms of Inconel 718 alloys subjected to varying degrees of rolling deformation. The results show that the strain energy increases with rolling deformation, enhancing the driving force for δ phase formation during subsequent heat treatment. This promotes the precipitation of the δ phase, resulting in a reduction of the γ” phase within the alloy. Furthermore, the grain rotation mechanism induces a transition from random to preferred crystallographic orientation in the microstructure after creep deformation. Specifically, grains initially aligned along the 〈110〉 // rolling direction (RD) undergo rotation to 〈100〉 // RD and 〈111〉 // RD orientations, leading to a reduction in the <110> fiber component and an increase in the <100> and < 111> fiber components. Additionally, increased rolling deformation promotes stress concentration, elevates the kernel average misorientation (KAM) value, increases the prevalence of cleavage surfaces, and enhances the tendency for brittle fracture. Strict control over rolling deformation is crucial, as excessive deformation can markedly degrade creep properties. This study establishes a theoretical framework for optimizing the production of Inconel 718 alloys with superior high-temperature performance.