Effect of homogenizing heat treatment on the microstructure of new low-chromium alumina-forming austenitic steels
Year: 2025
Type: article
Abstract: In the present research work, microstructure evolutions of the new generation of low-chromium Alumina-Forming Austenitic (AFA) steel containing up to 8 wt. % aluminum were investigated. For this purpose, samples with 0, 4, 6, and 8 wt. % aluminum were cast and homogenized at 1200°C for 4 hours. The alloys were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), dilatometry analyses, and hardness tests in both as-cast and homogenized conditions. The results indicate that adding up to 4 wt. % aluminum resulted in a fully austenitic microstructure, while an increase up to 8 wt. % led to a dual-phase ferritic-austenitic microstructure. During the homogenization heat treatment process, the delta-ferrite phases were dissolved in the matrix, resulting in a more uniform microstructure. Furthermore, adding aluminum decreases the coefficient of thermal expansion (CTE) and increases the austenite lattice parameter by diffusion of Al and Ni from delta-ferrite to austenite. Moreover, as the aluminum content increased from 0 to 8 wt. %, the hardness of the alloys increased from 93 to 258 HBW for as-cast alloys and 112 to 234 HBW for homogenized alloys.
Authors: Mohammad Mehdi Khalvan, Seyed Mohammad-Ali Boutorabi, Mehdi Diavandari
Institution: Iran University of Science and Technology
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,640
OpenAlex ID: W4409074070