Impact of Partitioning Temperature Parameters during the Quenching and Partitioning Process on Medium Carbon Steels with Two Different Alloying Strategies

Quenching and partitioning (Q&P) heat treatments have recently gainedattention as promising methods for the third generation of advanced high-strength steels, particularly in industrial applications like automotive. This studyinvestigates the microstructural evolution during Q&P in two medium-carbonhigh-silicon and aluminum-alloyed steels, exploring potential additional phasetransformations controlling the final structure. The choice to focus on Si andAl- medium-carbon steel is linked to the lower cost of these elements compared tocommonly alloying elements like Ti, Cr, Mo, and V, while still achieving highmechanical properties through Q&P. The Q&P process is analyzed by varying thevolume fraction of primary martensite (M1) at 0.25, 0.50, and 0.75, with parti-tioning temperatures ranging from 350 to 550 °C for 30 min. At 350 °C, a significantvolume fraction of stabilized austenite (up to 0.3) is observed. However, concurrentreactions such as nanostructured bainite and martensite formation lead to devi-ations from the theoretical constrained carbon equilibrium (CCE). At highertemperatures (450–550 °C), tempering reactions, including cementite precipitationand pearlite formation, reduced the austenite final fraction. The study highlightsthat heat treatment design, particularly partitioning temperature, must be tailoredto the specific steel composition due to the varying effects of Si and Al.RESEARCH ARTICLE lwww.steel-research.desteel research int. 2024, 2400710 2400710 (1 of 13) © 2024 The Author(s). Steel Research International published by Wiley-VCH GmbH