Serrated flow and work-hardening behavior of China low activation martensitic steel (CLAM)

Abstract

Serrated flow and work-hardening behavior (by Voce equation) of China low activation martensitic (CLAM) steel were investigated in the temperature range of 300–923 K (27 °C to 650 °C). The steel exhibited serrated flow at intermediate temperatures of 573–623 K (300–350 °C) and elevated temperatures higher than 773 K (500 °C), respectively. Type A, A + B, A + C, A + D, and mild serrations were identified. The observed serrations, the plateau/peak in flow stress and a minimum in ductility suggested the occurrence of dynamic strain aging (DSA), a phenomenon due to interactions between solute atoms and dislocations during plastic deformation, at intermediate temperatures, while the mild serrations observed at high temperatures were ascribed to a combined effect of tensile deformation and dynamic recovery. The variations of work-hardening parameters including saturation stress σS, initial stress σI and rate parameter nV with respect to temperatures also implied the dominance of DSA at intermediate temperatures. CLAM steel in present investigation generally displayed two-stage work-hardening behavior consisting of transient stage and stage-III. Good correlations had been presented between work-hardening parameters obtained by Voce equation and the respective experimental tensile properties, suggesting adequate applicability of Voce relationship for CLAM steel.