The effect of strain path on material behaviour during hot rolling of FCC metals

Models representing material behaviour are now an essential component of the development process for rolled products. Although models based on physical parameters are being proposed, most current models employ empirical equations, which assume that the deformation can be characterized by the strain rate, temperature and the equivalent plastic strain. However, deformation in a flat product rolling pass involves a partial reversal of shear strain, and in long product and section rolling there are more complex changes in strain path in sequential passes. This paper briefly reviews the mapping of strain paths and their effects on the micromechanics of deformation and the resulting flow stress. The influence of ingrain heterogeneity of strain is discussed in relation to the development of dislocation structures and their effects on texture evolution and subsequent recrystallization behaviour. The effects on recrystallization kinetics and resulting grain size are sufficiently large to lead to significant errors in modelling the local behaviour in multipass rolling, if strain-path effects are not considered.