Abstract

n this research, hot deformation behavior of Nb-V microalloyed steel has been investigated by conducting hot compression tests at temperatures of 900-1100°C and under constant strain rates, ranging from 0.01 to 1^s-1. The stress-strain curves showed that dynamic recrystallization is responsible for flow softening at steady temperatures and strain rates. The relations between peak strain and peak stress with Zenner-Hollomon parameter, were developed and investigated via constitutive equations. The single peak and multiple peak flow curves at low and high Zenner regimes were observed and analyzed through later microstructural investigations. The values of apparent activation energy, strain rate sensitivity and stress exponent parameter were appraised to be 332, 0.18 and 5.6 kJ/mol, respectively. Microstructural investigations by optical microscopes were performed on deformed specimens to trace the occurrence of restoration processes.

Key words: Microalloyed steel, niobium, dynamic recrystallization, flow stress, carbonitride.