Plastic deformation and failure of TMCP S1100 ultrahigh-strength steel at elevated temperatures

This study investigates the influence of temperature on the plastic deformation and hardening behavior of Thermo-Mechanical Controlled Process (TMCP) S1100 ultrahigh-strength steel at different temperatures up to 900 °C. TMCP steels, recognized for their reduced carbon footprint and superior strength-to-weight ratio, are increasingly prevalent in structural engineering applications, necessitating a thorough assessment of their performance under fire conditions. The Swift and Voce constitutive models were evaluated for their efficacy in predicting plastic deformation across various temperatures. While both models captured the general stress–strain response, inconsistencies were observed at low and high strain levels. To address these limitations, a coupled Swift–Voce model was employed, yielding a more robust correlation between plastic strain and stress at elevated temperatures. Microstructural analyses clarified key hardening mechanisms, including dislocation multiplication, dynamic strain aging, dynamic recovery, martensite decomposition, and austenite formation, over the temperature range from room temperature to 900 °C. The observed agreement between the Voce and Kocks-Mecking models, both sensitive to microstructural evolution, substantiates the reliability of the derived correlations between the microstructure and hardening parameters. Finally, equations were proposed to establish the relationship between plastic deformation parameters and deformation temperature. These insights advance the understanding of TMCP S1100’s applicability for fire-resistant structural applications.