Effect of serrated flow on deformation behaviour of AISI 403 stainless steel

AISI 403, a martensitic stainless steel in the quenched and tempered condition has been subjected to uni-axial tension test at a range of strain rates (2 x 10(-5)-10(-2) s(-1)) and a range of temperatures (25-500 degreesC) to investigate the effect of temperature and strain rate on its mechanical properties. Serrated flow behaviour, predominately of type A and B, has been observed in the temperature range of 250-375 degreesC and at strain rates lower than 10(-3) s(-1) which suggests the presence of dynamic strain aging (DSA) in this parametric domain. In this domain, while an increase in ultimate tensile strength and work hardening have been observed, the yield strength has been found to be nearly independent of temperature. A loss in ductility, due to the presence of DSA has also been seen in this material. The solute responsible for serrated flow has been identified to be chromium, which is the major alloying addition in this material. McCormick's method has been employed to determine the activation energy from the knowledge of critical strain for the appearance of serrations as a function of strain rate and temperature. The magnitude of activation energy is approximately 50% of that for bulk diffusion of chromium in body centered cubic iron suggesting that a mechanism other than volume diffusion is involved. (C) 2000 Elsevier Science S.A. All rights reserved.