A study of coarsening, recrystallization, and morphology of microstructure in Al-Sc-(Zr)-(Mg) alloys

Minor additions of Sc are effective in controlling the recrystallization resistance of 5xxx, 2xxx, and 7xxx aluminum. The addition of Sc to aluminum results in the rapid precipitation of homogeneously distributed Al3Sc dispersoids, which are coherent with the matrix and have the Ll(2) structure. The presence of Al3Sc dispersoids increases the recrystallization resistance of wrought alloys. The higher coarsening rate of Al3Sc compared to that of Al3Zr may limit its applications as a single ancillary addition. When both scandium and zirconium are used in the same alloy, Al-3(Sc1-x, Zr-x) dispersoids form. These dispersoids are more effective recrystallization inhibitors than either Al3Sc or Al3Zr. The Al-3(Sc1-x, Zr-x) dispersoids precipitate more rapidly than Al3Zr but have a slower coarsening rate than Al3Sc. Furthermore, the distribution of Al-3(Sc1-x, Zr-x) is significantly more homogeneous than Al3Zr. It was also established that alloys containing up to 3.5Mg showed improvement in recrystallization resistance when both Sc and Zr were present. Several morphologies of Al3Sc and Al-3(SC1-x, Zr-x) were also observed.