Aerospace and automotive aluminum alloys include peritectic elements such as Ti and Zr to control the as-cast grain size and to prevent recrystallization in downstream operations. Al3Ti intermetallics are commonly found at the interface of TiB2 refiner particles and the α-Al phase. Al3Zr intermetallics have also been identified as nucleant particles of α-FCC grains within the 6082 Aluminum Alloy. Besides Ti and Zr, Si is usually present as an impurity or alloying element in aluminum alloys. While the mutual substitution of Zr and Ti into the Al3Zr-D023 and Al3Ti-D022 phases has been extensively reported in the literature, the substitution of Si inside these intermetallics is not clear. Here, in situ precipitation of Al3Zr/Al3Ti-based intermetallics was performed during the solidification of Al-Si-Zr-Ti model alloys. A combination of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Electron Microprobe (EMP) analysis revealed the presence of both intermetallics concentrated inside an α-FCC matrix. Energy Dispersive X-Ray Analysis (EDX) confirmed that Zr and Ti substitute each other in the tetragonal phases, whereas Si substitutes mainly for Al sublattice sites. Finally, the substitution of Si within both (Al,Si)3(Ti)-D022 and (Al,Si)3(Zr)-D023 phases was investigated by means of first-principles calculations.

Moderated by: Hideyuki Yasuda