Solution treatment modifies microstructure and enhances properties in austenitic steel, indicating optimal temperatures for performance.
In this study, an as-cast Fe-18Ni-14Cr-4Mo-2Nb-3Al alumina-forming austenitic (AFA) steel was subjected to the solution treatment from 1100°C to 1300°C, and the microstructure and mechanical properties with temperature were systematically studied. The results indicate that AFA steels are fully austenitised after solution treatment at 1100–1200°C. As the solution temperature increases from 1100°C to 1200°C, the grain size grows from 15.5 μm to 20.4 μm, and the second-phase content inside decreases from 4.0% to 2.8%. These microstructural changes lead to a decrease in microhardness from 197.9 HV0.2 to 170.1 HV0.2 and a reduction of tensile yield strength from 268 MPa to 208 MPa, thus increasing elongation from 26% to 32%. However, when treated at 1300°C, the microhardness and strength increase to 179.0 HV0.2 and 730 MPa, with the elongation increasing to 46%, because of the new δ-ferrite formed.
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Li et al. (2025) studied this question.