Hot deformation behavior of austenite in HSLA-100 microalloyed steel

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 528; no. 4; pp. 2158 - 2163
• Main Authors: Momeni, A., Arabi, H., Rezaei, A., Badri, H., Abbasi, S.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.02.2011; Elsevier
• Subjects: Applied sciences; Carbon; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Cu-bearing HSLA steel; Dynamic recrystallization; Elasticity. Plasticity; Elongation; Exact sciences and technology; Flow curve; Flow stress; High strength low alloy steels; Hot compression; HSLA-100; Materials science; Mathematical analysis; Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Physics; Treatment of materials and its effects on microstructure and properties; Yield point; Yield strength; Cu-bearing HSLA steel; Dynamic recrystallization; Hot compression; Flow curve; HSLA-100; Hot deformation; Constitutive equation; Dislocation motion; Work hardening; Plastic flow; Compressive testing; Dynamical recrystallization; Low alloy steels; Bearing steel; Microalloyed steel; Transition elements; Viscoplasticity; Yield strength; Microstructure; Zener Hollomon parameter; High-strength steels; Elongation (mechanics); Flow stress; Strain rate
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2010.11.062

▶ The flow stress is well fitted by the exponential constitutive equation. ▶ The average value of apparent activation energy for hot deformation is 377 kJ mol −1. ▶ A yield point phenomenon is observed on flow curves at high temperatures. ▶ The Avrami exponent is determined around unity for dynamic recrystallization. Dynamic recrystallization of austenite in the Cu-bearing HSLA-100 steel was investigated by hot compression testing at a temperature range of 850–1150 °C and a strain rate of 0.001–1 s −1. The obtained flow curves at temperatures higher than 950 °C were typical of DRX while at lower temperatures the flow curves were associated with work hardening without any indication of DRX. At high temperatures, flow stress exhibited a linear relation with temperature while at temperatures below 950 °C the behavior changed to non-linear. Hence, the temperature of 950 °C was introduced as the T nr of the alloy. All the flow curves showed a yield point elongation like phenomenon which was attributed to the interaction of solute atoms, notably carbon, and moving dislocations. The maximum elongation associated with the yield point phenomenon was observed at about 950 °C. Since the maximum yield point elongation was observed about the calculated T nr, it was concluded that carbon atoms were responsible for it. It was also concluded that the temperature at which the yield point elongation reaches the maximum value increases as strain rate rises. The stress and strain of the characteristic points of DRX flow curves were successfully correlated to the Zener–Hollomon parameter, Z, by power-law equations. The constitutive exponential equation was found more precise than the hyperbolic sine equation for modeling the dependence of flow stress on Z. The apparent activation energy for DRX was determined as 377 kJ mol −1. The kinetics of DRX was modeled by an Avrami-type equation and the Avrami's exponent was determined around 1.1.