Formation of metastable L1<inf>2</inf> phases in Al<inf>3</inf>Zr and Al-12.5%X-25%Zr (X ≡ Li, Cr, Fe, Ni, Cu)

The intermetallic Al3Zr crystallizes in the tetragonal DO23 structure but can be produced as a metastable cubic L12 structure by rapid solidification. We have studied the effects of mechanical alloying, a low-temperature isothermal processing method, and ternary additions of lithium, chromium, iron, nickel and copper on the phase stability of the L12 phase. Mechanically alloyed Al3Zr is single-phase L12 which is stable up to 550 °C. The additions of lithium or chromium increase the stability of the L12 phase to 750 and 740 °C, respectively. The addition of iron or nickel leads to the formation of amorphous, rather than L12, phases. Mechanically alloyed Al-12.5%Cu-25%Zr is single-phase L12 and this phase is stable up to at least 1300 °C. © 1991.