Effects of temperature and strain rate in strain hardening in torsion of a twinning-induced plasticity steel

A series of torsion tests were performed to characterise the plastic response at high strain levels in a twinning-induced plasticity steel (22%Mn-0.6%C in mass) in the interval of temperatures 20 degrees C <= T <= 450 degrees C at three different shear strain rates, , 2.4 center dot 10(-3), 0.2, 6.5 s(-1). The work hardening at room temperature was near-linear typical of this steel. It was found that the work hardening rate and the torsional ductility are strongly influenced by temperatures T >= 150 degrees C. Sub-surface deformed specimens at T = 450 degrees C and 2.4 center dot 10(-3) s(-1) were analysed via high-resolution electron backscatter diffraction system, showed a sub-structure of very fine grains indicating that continuous dynamic recrystallization had taken place.