Microstructural evolution and mechanical property of Al-Zr and Al-Zr-Y alloys

Microstructure and mechanical property of Al-0.30Zr, Al-0.30Zr-0.08Y and Al-0.30Zr-0.16Y (wt%) alloys were investigated. Minor addition of Y refines the grain size and forms the eutectic Al3Y phase particles within grains and at grain boundaries in as-cast Al-Zr-Y alloys. The increase of Y additions results in larger amount and particle size of Al3Y in Al-Zr-Y. The decomposition of solid solution leads to a high number density of secondary L12-structured Al3(Zr,Y) precipitates within dendritic regions in Al-Zr-Y during isothermal aging at 450 °C. The precipitate-free regions in grains and adjacent to grain boundaries in Al-Zr-Y alloys are narrower than that in Al-Zr. The mechanical property of Al-Zr alloys gets improved with increasing Y-content. The Al-0.30Zr-0.08Y alloys show improved recrystallization resistance compared with Al-0.30Zr. However, excess Y-addition, e.g. 0.16%, is detrimental to the recrystallization resistance of Al-Zr alloys due to the particle simulate nucleation (PSN) induced by micron-sized Al3Y phase.