Effect of temperature on the plastic flow and strain hardening of direct-quenched ultra-high strength steel S960MC: Fid-Bau Portal

Effect of temperature on the plastic flow and strain hardening of direct-quenched ultra-high strength steel S960MC

Ghafouri, Mehran / Afkhami, Shahriar / Pokka, Aki-Petteri / Javaheri, Vahid / Togiani, Amir / Larkiola, Jari / Björk, Timo

Abstract

Highlights • Plastic deformation of the ultra-high strength steel S960MC is evaluated at different temperatures up to 900 ℃. • The hardening behavior is modeled via Hollomon and Voce equations to compare the hardening parameters quantitatively. • The Voce equation has proven capable of modeling the hardening and flow behavior through the whole temperature range. • Microstructural investigation parallel to tensile tests established correlations between the hardening parameters and microstructural features. • The dominant deformation mechanism changed per deformation temperature from dislocation interactions to dynamic strain aging, dynamic recovery, and phase transformations.

Abstract This study investigates the plastic deformation and hardening behavior of the direct-quenched ultra-high strength steel S960MC at various temperatures ranging from room temperature to 900 ℃. In this regard, the Hollomon and Voce equations are used to model the hardening behavior of the material at different temperatures. The suitability of each equation to predict the plastic flow of S960MC is evaluated based on the best resulted fit for the material. In addition, microstructural investigations are carried out to indicate the correlations between the microstructural changes, occurring in the range of room temperature to 900 ℃, and hardening behavior and governing parameters. The Hollomon approach showed deviations from the experimental results for room to intermediate temperatures; however, the Voce equation modeled the material's strain hardening and flow behavior more successfully for the entire temperature range of room temperature–900 ℃. Additionally, there was a significant consistency between the Kocks-Mecking and Voce parameters. Dislocation interactions, dynamic strain aging, dynamic recrystallization, dynamic recovery, tempering (martensite decomposition), and austenite formation were the most influential microstructural features on the hardening behavior at various temperatures. The correlations between these microstructural features and hardening parameters were established satisfactorily for both the Hollomon and Voce approaches.