Dynamic recrystallization during hot deformation of aluminum: a study using processing maps

Abstract

The hot deformation behavior of aluminum of different purities has been studied in the temperature range of 250°C to 600°C and strain-rate range of 10^-3 to 10^-2 s^-1. On the basis of the flow stress data, the strain-rate sensitivity (m) of the material is evaluated and used for establishing power dissipation maps following the Dynamic Materials Model. These maps depict the variation of the efficiency of power dissipation [η=2m/(m+1)] with temperature and strain rate. A domain of dynamic recrystallization (DRX) could be identified in these maps. While the strain rate at which the efficiency peak occurred in this domain is 10^-3 s^-1 the DRX temperature is purity dependent and is 375°C for 99.999 pct Al, 450°C for 99.995 pct Al, 550°C for 99.94 pct Al, and 600°C for 99.5 pct Al. The maximum efficiency of power dissipation for DRX in aluminum is about 55 pct. The sigmoidal increase of grain size with temperature in the DRX domain and the decrease in the DRX temperature with increase in the purity of aluminum are very similar to that observed in static recrystallization, although DRX occurred at much higher temperatures.