Heat Treatment and Austenitization Temperature Effect on Microstructure and Impact Toughness of an Ultra-High Strength Steel

• Main Authors: Daniel M. Field, Stephen R. Cluff, Krista R. Limmer, Jonathan S. Montgomery, Daniel J. Magagnosc, Kyu C. Cho
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Metals
• Subjects: ultra-high strength steels; AF9628; plate steel; toughness; heat treatment
• Online Access: https://www.mdpi.com/2075-4701/11/5/723

Heat treatment parameters were varied to determine the effect of normalizing and austenitizing temperature on the properties of an ultra-high strength wrought steel. Normalizing temperature did not have a significant effect on strength and ductility. Higher normalizing temperatures led to an increase in final prior austenite grain size and a slight loss in toughness. Austenitizing temperature of 825 °C was insufficient to produce a fully austenitic structure prior to quenching and led to sub-par impact behavior. The best properties were obtained after austenitizing at 915 °C followed by water quenching; the resulting quasi static properties were shown to be a yield strength of 1380 MPa with an ultimate tensile strength of 1670 MPa and 12.5% total ductility. Charpy V-notch impact properties as high as 52 J at −40 °C and 75 J at 25 °C and the behavior were achieved using higher austenitizing temperatures as well.