Lattice matching of D023 and D022 phases in Al-6at.%(Ti,V,Zr) systems

Composite quaternary alloys with 21–22 vol.% of Al3M (M = Ti,V,Zr) were made by vacuum arc melting. Two inlermetallic phases were found in alloys: one is V rich D022-Al3(Ti,V,Zr) and the other is Zr rich D023-Al3(Ti,V,Zr). Measured lattice constants of precipitate phases were strongly dependent on the composition of transition elements in precipitates and generally obeyed Vegardʹs rule. The lattice misfits between Al3M phases and the matrix did not change much in alloys while the lattice misfit between D022 and D023 Al3M phases was found to decrease with an increase in Ti content implying that the interface between both phases became more smooth, hard to distinguish and separate. A geometrical model was made for the lattice matching between two, D022 and D023 Al3M phases. Titanium has been found to act as a retarding element to separation into D023 and D022 phases and the pre-existing phase may have been L12 or D023 phase.