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

Abstract

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 Al 3 Sc dispersoids, which are coherent with the matrix and have the L1 2 structure. The presence of Al 3 Sc dispersoids increases the recrystallization resistance of wrought alloys. The higher coarsening rate of Al 3 Sc compared to that of Al 3 Zr may limit its applications as a single ancillary addition. When both scandium and zirconium are used in the same alloy, Al 3 (Sc 1-x , Zr x ) dispersoids form. These dispersoids are more effective recrystallization inhibitors than either Al 3 Sc or Al 3 Zr. The Al 3 (Sc 1-x , Zr x ) dispersoids precipitate more rapidly than Al 3 Zr but have a slower coarsening rate than Al 3 Sc. Furthermore, the distribution of Al 3 (Sc 1-x , Zr x ) is significantly more homogeneous than Al 3 Zr. 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 Al 3 Sc and Al 3 (Sc 1-x , Zr x ) were also observed.

Precipitate-induced nonlinearities of diffusion along grain boundaries in Al-based alloys

“…The resulting misfit at the relevant annealing temperatures 773-823 K yields a calculated critical radius between 23-26 nm for Al 3 Sc [using Eq. (B3)], agreeing well with our experimentally observed range of 20-30 nm and the previously reported values [48,[50][51][52][53][54][55]. The critical particle size is found to increase with temperature, a trend consistent with the Al/Al 3 Sc lattice misfit which decreases with temperature.…”

High strain rate superplasticity of an 1570C aluminum alloy with bimodal structure obtained by equal-channel angular pressing and rolling

“…Такое поведение сплава, по всей видимости, обусловлено активизацией процессов динамической рекристаллизации с ростом температуры испытания. Указанная немонотонная за-висимость положения оптимума сверхпластичности от температуры деформации вызвана тем, что присут-ствующие в сплаве нанодисперсные алюминиды пере-ходных металлов, Al 3 (Sc,Zr), обладают довольно высо-кой термической стабильностью лишь до температур 450-475°C [20,21]. Поэтому, когда плотность этих частиц наибольшая, и они когерентны матрице (что имеет ме-сто при низких температурах испытаний), то, взаимо-действуя с решеточными дислокациями, такие частицы интенсивно подавляют процессы возврата и рекристал-лизации, препятствуя тем самым формированию одно-родной мелкозернистой структуры в процессе сверхпла-стической деформации.…”

Developing Sc and Zr containing Al-B C metal matrix composites for high temperature applications /

“…Al-Sc systems in terms of decreasing the coarsening rate [72,107], increasing the strength and the recrystallization resistance [23,113,114].…”

“…was described to be spherical [113,116]. Raju et al [119] and Yu et al [120] independently observed cubic morphologies of A^Sci-jZr*) precipitates.…”