Effect of Nb-V microalloying on hot deformation characteristics and microstructures of Fe-Mn-Al-C austenitic steel

Abstract

The flow behavior and microstructure of Fe-Mn-Al-C austenitic steel and Nb-V microalloyed Fe-Mn-Al-C austenitic steel during uniaxial hot compression deformation are systematically studied in the present paper. The flow curves of both steels are analyzed, as well as constitutive equations and processing maps are established. The results reveal that the flow softening phenomenon of Nb-V microalloyed Fe-Mn-Al-C austenitic steel is more significant at low temperatures and low strain rates. Moreover, the hot deformation activation energy of Fe-Mn-Al-C steel is marginally affected by the addition of Nb-V. The uniformly distributed nano-sized (Nb,V)C particles, which precipitate in Nb-V microalloyed Fe-Mn-Al-C steel, act as the nucleation sites for dynamic recrystallization (DRX). These particles promote the DRX and pin the grain boundaries to restrain the growth of DRX grains. Nb-V microalloying renders a positive influence on the hot deformation stability of Fe-Mn-Al-C steel and broadens the optimum hot processing window. Based on the processing map and microstructure, the optimum hot processing windows of Nb-V microalloyed Fe-Mn-Al-C steel at the strain of 0.7 are determined as 894–1025 °C/0.01–0.14 s −1 and 1050–1200 °C/0.03–0.95 s −1 . • Effect of Nb-V microalloying on hot deformation characteristics and microstructures in Fe-Mn-Al-C steel was studied. • Nb-V led to flow softening of Fe-Mn-Al-C steel at low temperatures and low strain rates. • Nb-V improved the hot deformation stability of Fe-Mn-Al-C steel. • Nb-V increased the nucleation sites for dynamic recrystallization of Fe-Mn-Al-C steel.