Structural and phase transformation in a TWIP steel subjected to high pressure torsion

We report on the changes in microstructure and phase composition in a high-Mn steel due to severe plastic deformation realized via high pressure torsion at different temperatures. Severe straining conducted at 20 degrees C and 300 degrees C allowed producing nanostructural states with a mean grain size less than 100 nm. Besides, straining at room temperature leaded to formation of strain-induced e-martensite while at 300 degrees C fully austenite state was produced. Despite the revealed differences both states demonstrated similar, notably increased level of hardness up to similar to 580 Hv. (C) 2015 Elsevier B.V. All rights reserved.1199sciescopu