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

Models representing material behaviour are now an essential component of th e development process for rolled products. Although models based on physica l parameters are being proposed, most current models employ empirical equat ions, which assume that the deformation can be characterized by the strain rate, temperature and the equivalent plastic strain. However, deformation i n 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 s train 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 influ ence of ingrain heterogeneity of strain is discussed in relation to the dev elopment of dislocation structures and their effects on texture evolution a nd subsequent recrystallization behaviour. The effects on recrystallization kinetics and resulting grain size are sufficiently large to lead to signif icant errors in modelling the local behaviour in multipass rolling, if stra in-path effects are not considered.