Plastic flow and failure of plain carbon steels in ferrite + austenite region

Abstract

The temperature dependence of the flow stress of the α+γ mixture ofplain carbon steels has been measured. An observed flow-stress minimum in the temperature range of the mixture expands with decreasing carbon content. The general features of this behaviour are predicted by a simple-mixture model, but a more detailed approach should accommodate the heterogeneous deformation within the mixture. Because the work hardening is different in the a and γ components, the work hardening of the mixture varies throughout its temperature range. For the failure behaviour, uniform deformation of the two-phase specimens is extended beyond the Considere condition. An examination offracture data shows that in low-carbon steels a unique form of embrittlement, restricted to the temperature range of the two-phase mixture, is increased when the austenite is strengthened by an aluminium addition and relatively large sulphide inclusions are present in the weaker ferrite component.