Dynamic materials modelling concepts applied to analysis of hot rolling of commercial aluminium alloys

Abstract

A typical industrial hot rolling operation applied to a commercial Al–1%Mg alloy has been analysed in terms of some concepts from dynamic materials modelling (DMM), particularly the so called dissipator co-content J and the efficiency of power dissipation through microstructural changes η. The calculation of the parameter η for every deformation condition of the hot rolling schedule has been conducted assuming that this variable depends not only on the mean deformation temperature and strain rate but also on the strain applied to the material. All the analysis has been conducted on the basis of a constitutive equation previously determined for this material on a rational basis, which is capable of describing the strain, strain rate, and temperature dependence of the flow stress. It has been determined that, for this material, η can be significantly dependent on strain under certain deformation conditions, particularly low deformation temperatures and relatively high strain rates. It has also been shown that for the materials analysed, η is much more dependent on deformation temperature than on strain rate. A comparative analysis carried out with aluminium of various purities indicates that η is much lower for the alloy when it is deformed under similar conditions. In this sense, it has been suggested that such results could be interpreted in terms of the impurity content of the material and the interaction of the alloying atoms with the dislocation structure developed during high temperature deformation. However, this is only possible if the hypothesis advanced by Prasad and co-workers, that the power dissipation efficiency is associated with the dynamic microstructural processes that occur during deformation, is considered valid. The present results indicate that, contrary to previous findings, in terms of DMM concepts there are no specific conditions of temperature and strain rate for the optimum processing of the materials investigated.