Development of a predictive model for the mechanical properties of heat-treated AISI 4340 steel and its optimization

Document Type

Article

Publication Title

Journal of Materials Research and Technology

Abstract

AISI 4340 steel is widely used in aerospace, automotive, and energy applications due to its high strength and toughness, which can be tailored through heat treatment. This study investigates the influence of annealing, normalizing, and oil quenching parameters on the microhardness and impact energy of AISI 4340 steel and develops regression-based predictive models to describe these relationships. Heat treatments were performed at 900, 925, and 950 °C for 1, 1.5, and 2 h, and mechanical properties were analyzed using Vickers microhardness and Charpy impact tests. Statistical analysis through ANOVA and response surface optimization identified the most influential factor as temperature, contributing over 90 % to microhardness and 60–80 % to impact energy variation. Optimal parameters were found to be 908.7 °C/2 h for annealing, 905 °C/1.75 h for normalizing, and 912.55 °C/2 h for oil quenching, yielding microhardness values of 221 HV, 270 HV, and 506 HV, and impact energies of 45 J, 51 J, and 33 J, respectively. The composite desirability indices (D) were 0.5991, 0.5759, and 0.7894, confirming balanced optimization between microhardness and impact energy. The regression models (R2 = 85–99 %) demonstrate strong internal consistency within the studied parameter range. These results provide quantitative insight into the temperature–time–property relationship in AISI 4340 steel and support optimized heat treatment design for structural applications.

First Page

6191

Last Page

6198

DOI

10.1016/j.jmrt.2025.11.014

Publication Date

11-1-2025

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