Effect of solute impurities on the rate of recovery and recrystallization in a 1050 aluminum hot rolled sheet

The effect of soaking conditions of ingots on the rate of recovery and recrystallization in a 1050 hot-rolled sheet during annealing at 350°C was investigated. The rate of recovery and recrystallization in no soaking and 600°C/8 h WQ (water quenching) was slower than that of 450°C/8 h FC (furnace cooling). Many solute impurities (Fe, Si), which were contained in no soaking and 600°C/8 h WQ cause the delay of recovery and recrystallization. Particularly, in no soaking, no precipitation was observed within grains of the ingot and the hot-rolled sheet. On the other hand, in 450°C/8 h FC, the recovery and recrystallization is too fast. Fine granular precipitates with less than 0.1 µm in diameter were observed and solute impurities were few in the ingot and the hot-rolled sheet. The pinning of sub-grain boundaries by these fine precipitates was not observed. The normalized change of Vickers hardness and electrical resistivity was divided into a recovery reaction and a recrystallization one respectively by a new developed rate equation. The role of impurities in the recovery and recrystallization was explained and made clear by the obtained values of parameters in this equation.