Improving Recrystallization Resistance in Wrought Aluminum Alloys with Scandium Addition

摘要

The 5xxx, 2xxx, and 7xxx aluminum alloys can all benefit from minor additions of Sc to control recrystallization. The addition of Sc rapidly precipitates high volume fraction of homogeneously distributed dispersoids having coherent Al_3Sc (Ll_2) structure. Al_3Sc dispersoids impart some improvement in recrystallization resistance to wrought alloys, namely with higher annealing temperatures and volume fractions, compared to alloys employing Al_3Zr. However, the higher coarsening rate of Al_3Sc compared to that of Al_3Zr may limit its usability. When both scandium and zirconium are used in the same alloy Al_3(Sc_(1-x), Zr_x) dispersoids form, which are more effective than either Al_3Sc or Al_3Zr acting alone. The Al3(Sc_(1-x), Zr_x) dispersoid benefits from the rapid precipitation characteristic of Sc in Al, the slow coarsening associated with Zr, and a high volume fraction as an effect of both Sc and Zr. Furthermore the distribution of Al_3(Sc_(1-x), Zr_x) is homogeneous. It was also established that alloys containing up to 3.5Mg showed improvement in recrystallization resistance with both Sc and Zr present.