Dynamically recrystallized microstructures, textures, and tensile properties of a hot worked high-Mn steel

Abstract

The deformation microstructures and mechanical properties were studied in a high-Mn steel subjected to hot compression. The deformation microstructures resulted from the development of dynamic recrystallization (DRX). Two DRX mechanisms, namely discontinuous and continuous, operated during warm-to-hot working. Under the conditions of hot working when the flow stresses were below 100 MPa, a power law function was obtained between the DRX grain size and the true flow stress with a grain size exponent of −0.8 owing to the discontinuous DRX. On the other hand, the gradual change in the operating DRX mechanism from a discontinuous to continuous one upon a transition from hot to warm working, when the true flow stress increases above 100 MPa, resulted in the grain size exponent of about −0.5 in the power law between the flow stress and the DRX grain size. The DRX microstructures developed by warm-to-hot working provide a beneficial combination of mechanical properties including high ultimate tensile strength in the range of 700–900 MPa and sufficient ductility with a uniform elongation well above 50%. The strengthening of the samples with DRX microstructures was attributed to the combined effect of the grain size and dislocation strengthening resulting in a rather high grain boundary strengthening factor of 570 MPa µm0.5 in the Hall-Petch-type relationship.