Boron Effect on the Softening Parameter (Ω) of Advanced Ultra-High Strength Steels (A-UHSS) under Uniaxial Hot-Compression Conditions

Abstract

ABSTRACTAdvanced ultra-high strength steels (A-UHSS) are revolutionizing both the steel and automotive industries, therefore it is imperative to study their hot plastic deformation behavior and modeling. The flow characteristics of all hot forming processes consist basically of two competitive phenomena: strain hardening and softening due to dynamic mechanisms (recovery and/or recrystallization). In this research work, the softening parameter was determined in a low carbon A-UHSS microalloyed steel with different amounts of boron (0, 14 and 214 ppm). Experimental stress–strain data of uniaxial hot-compression tests at different temperatures (950, 1000, 1050 and 1100 °C) and strain rates (10–3, 10–2 and 10–1 s–1) were used. The stress–strain relationships as a function of temperature and strain rate were described on the basis of the Estrin, Mecking, and Bergström model. The experimental values of the softening parameter Ω were adjusted using the least-squares method. In general, the results reveal that the softening parameter increases with increasing boron content.