Temperature effect on twin formation kinetics and deformation behavior of Fe-18Mn-0.6C TWIP steel

Temperature effect on deformation behavior has been investigated in relation to formation kinetics of twins in a Fe-18Mn-0.6C TWIP steel. Total elongation was found to reach a maximum value of 88% at 200 A degrees C and then decreased continuously with the increase in test temperature from 300 A degrees C up to 600 A degrees C. This reversed temperature dependence on ductility could be attributed to the formation kinetics of deformation twins, as was prescribed by an internal variable theory of inelastic deformation. It was found that twins became more difficult to form at higher temperatures due to insufficient internal strain energy accumulated to reduce ductility progressively in this temperature range. Dislocation glide mechanism became, however, dominant at higher temperatures above 600 A degrees C to increase total elongation following the usual temperature dependence. Finally the stacking fault energy was related with the stability parameter, beta, used in the transformation kinetics relation.