Document Type : Research Article

Authors

• Shima Pashangeh ¹
• Seyyed Sadegh Ghasemi Banadkouki ²

¹ Department of Materials Engineering, Yasouj University.

² Department of Mining and Metallurgical Engineering, Yazd University

Abstract

Third-generation advanced high-strength steels serve as advanced engineering materials in various industries, including land, air, rail, and maritime transportation, with expanding applications. In the present study, a sample of low-alloy steel with medium carbon content (0.529 wt%) and high silicon content (1.670 wt%) was selected and subjected to one-step quenching and partitioning heat treatment at temperatures of 140 and 180 oC for different partitioning times (isothermal holding for redistribution of carbon element between initial martnsite and untransformed austenite). Phase transformations and microstructural investigations were conducted using dilatometry, laser microscopy, and Electron Backscatter Diffraction (EBSD) analysis. Dilatometry results indicated that the formation of initial martensite occurs at a temperature of 275 oC, and during a holding time of 3600 s, only carbon partitioning into retained austenite takes place at temperatures of 140 and 180 oC, yet martensite formation occurs during the final cooling. Additionally, considering the changes in specimen width during isothermal holding, tempering of the initial martensite can be anticipated. Microstructural examinations also confirmed the formation of microphasic structures, including initial martensite, retained austenite, and final martensite.

Keywords

• Low alloy steel
• Advanced high strength steels
• Quenching and partitioning heat treatment
• Phase transformation
• Dilatometry test

Main Subjects

• Heat treatment and thermo-mechanical processes