Abstract
The influence of grain size on the flow stress of a duplex austenitic–ferritic steel was examined at room temperature. Three groups of specimens, the steels in each group containing about the same amount of the phases, i.e. 26, 35, and 47%α, but having different grain sizes, were investigated. As in single phase metals and alloys and two phase dispersion alloys, a relationship of the Hall–Petch type can be used to describe the dependence of flow stress on the grain size of the duplex alloy. The traditional exponent m = 0·5 can be replaced by m = 1. The structural changes of the austenite and ferrite during deformation were observed and the dislocation densities were measured for small strains. Observations by electron microscopy showed that the dislocation density was higher in the vicinity of grain boundaries than within the grains and was not dependent on grain size.
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