STATIC RESTORATION OF ALUMINUM DURING MULTISTAGE HOT-ROLLING SIMULATION

The static softening of aluminium between the deformation steps of mul ti-stage hot torsion tests has been investigated by analysing the temp erature behaviour of the mean flow stress a and the fractional softeni ng x(s) throughout the hot rolling simulation. The numerous items of i nformation which the <(sigma)over bar> - 1/T and x(s) - T diagrams con tain were examined. Four distinct regions of static restoration have b een found which display different softening behaviour, depending on th e duration of the inter-pass time and the strain per pass. Additionall y, the evolution of the microstructure during multistep deformation wa s examined by SEM. On the basis of the fractional softening, a retaine d strain epsilon(r) has been derived which describes the predeformed s tructure entering a succeeding deformation pass due to incomplete stat ic restoration during the preceding arrest interval.