Hot deformation and static softening behavior of vanadium microalloyed high manganese austenitic steels

The hot deformation and static softening behavior of various high Mn (20-30 wt%) austenitic steels microalloyed with different V (0.1, 0.2 wt%), C (0.2, 0.6, 1 wt%) and N (0.005-0.025 wt%) contents were investigated. Double-hit torsion tests at temperatures in the range 700-1100 °C were carried out and specimens quenched at selected conditions were examined using advanced microscopy techniques (EBSD-TEM) to characterize the recrystallization and strain-induced precipitation behavior. The results show that precipitation of vanadium at the hot working temperature range is sluggish. It mainly occurs for the combinations of 20%Mn-0.6%C-0.2%V and 30%Mn-1%C-0.1%V. When the carbon content is reduced to 0.2%C, strain-induced precipitation is suppressed at typical hot working temperatures, independently of the N level. The flow stress behavior was affected by the amount of C and by modifying the base composition from 30%Mn to 20%Mn-1.5%Al. However, the effect is complex and depends on deformation conditions. In the absence of strain-induced precipitation, the static softening kinetics was accelerated by increasing C content. However, no effect of Mn or V in solid solution was observed. In those cases where strain-induced precipitation took place, static recrystallization was severely delayed, leading to a major contribution of recovery to softening kinetics.