Effect of cold rolling on the aging kinetics of Al₂O₃/6061 Al composite

In this work, the effect of the degree of cold rolling on the aging kinetics of a 6061 Al alloy, and its composite with 15 volume % of Al₂O₃ reinforcement, have been studied. Isothermal aging was carried out at temperatures ranging from 160 to 190 °C. The results showed that the time to reach peak aging hardness for both Al alloy and its composite was accelerated by cold rolling. With an increase in the degree of cold rolling, the difference in hardness between the cold-rolled materials and the materials after peak aging decreased. The dislocations introduced by cold rolling played a major role in influencing the aging response. Both Al alloy and composite were found to have the same aging sequence of precipitation. The addition of Al₂O₃ in the Al alloy did not change the sequence of the precipitation reaction. However, the rate of the metastable phase precipitation can be assisted by cold rolling. The degree of cold rolling did not influence the reaction rate significantly, despite the value of the reaction temperature is decreased with increasing degree of deformation. On the contrary, as the cold-rolled reduction increases, the amount of precipitates reduced significantly.