Effect of Dissolved Impurities on the Rate of Recovery and Recrystallization in an A1050 Aluminum Hot-Rolled Sheet

The effect of the soaking conditions of ingots on the rate of recovery and recrystallization in an A1050 hot-rolled sheet during annealing at 350 degrees C was investigated. The rate of the recovery and recrystallization with no soaking and 600 degrees C/8 h WQ (water quenching) was slower than that of 450 degrees C/8 h FC (furnace cooling). Many dissolved impurities (Fe, Si), which were contained in the no soaking and 600 degrees C/8h WQ conditions cause the delay in the recovery and recrystallization. Particularly, in the no soaking condition, no precipitation was observed within the grains of the ingot and the hot-rolled sheet. On the other hand, in the 450 degrees C/8 h FC condition, the recovery and recrystallization was too fast. Fine granular precipitates of less than 0.1 mu m in diameter were observed and there were few dissolved impurities in the ingot and the hot-rolled sheet. Pinning of the subgrain boundaries by these fine precipitates was not observed. The normalized change in the Vickers hardness and electrical conductivity was divided into a recovery reaction and a recrystallization one, respectively, by a newly developed rate equation. The role of the impurities in the recovery and recrystallization was explained and clarified by the result of using this equation.