EFFECTS OF STRAIN-RATE AND TEMPERATURE ON DUCTILITY OF INTERSTITIAL-FREE STEEL SHEET

Effects of strain rate and temperature on tensile ductility of an interstitial free ultra low carbon steel sheet, which does not show dynamic strain aging have been studied. Total elongation of this steel decreases with an increase in strain rate up to 5 x 10(-2)/s and contrarily increases in the higher strain rate region. This increase of total elongation is due to a drastic increase of post-uniform elongation, which can be explained neither by heat generation due to plastic deformation nor by equivalency of temperature to strain rate. The possible mechanism for large post-uniform elongation in the high strain rate region is an increase in diffusion of local necking area due to grain boundary sliding.