Annealing Behavior of Cold-Rolled Inconel 601

Abstract

Present study investigates isothermal annealing behavior of prior cold-worked Inconel 601 (aka, IN 601) sheets. The study comprehensively covers the annealing response of the material over wide cold-reduction and temperature ranges. Using structural characterization and mechanical testing, the study tracks strain-hardening, strain-aging, recovery, and recrystallization stages of IN 601 sheets as a function of degree of cold-reduction and annealing temperature. Using X-Ray diffraction analysis, hardness measurements, and tensile tests, the study reveals that prior cold-worked IN 601, irrespective of the degree of cold-reduction, consistently exhibits strain-aging during low-temperature (~ 0.4T<inf>m</inf>) annealing. The investigation establishes that the ‘recovery stage’ is preceded by ‘strain-aging-stage’ during which the alloy exhibits superior strength and hardness than the strain-hardened and recovered states. Based on the thermomechanical experimental results, the current work proposes a recrystallization map that integrates the ‘strain-hardening’ and ‘strain-aging’ stages with the recovery and recrystallization stages. Additionally, microstructural analysis and SEM-EBSD analysis presented in this work indicate that, by suitably controlling strain-hardening and the recrystallization annealing, a refined microstructure comprising high aspect-ratio grains having high-angle grain-boundaries can be obtained that may improve both fatigue and creep properties of IN 601 sheets. © ASM International 2023.