Ternary phase diagram studies in Ti-Zr-Ni alloys

Equilibrium phase formation is reported for ternary Ti-Zr-Ni alloys near the i-phase-forming composition, for temperature slices between 500 and 700 degreesC. Selected microstructural results in as-cast and annealed samples are discussed. Dominant equilibrium phases identified are the C-14-like Laves phase, a Ti2Ni-like phase, alpha (Ti/Zr), the b.c.c. 1/1 W-phase and the i-phase. The i-phase forms over a small compositional range from a high-temperature equilibrium phase mixture of the Laves and alpha (Ti/Zr) solid solution phases. Lower annealing treatments have not been found to transform the i-phase, suggesting that in this alloy, the quasicrystal phase might be the ground state phase. Additions of small amounts of Pb and Pd, 1-2 at.%, are demonstrated to substantially effect the equilibrium phase formation for the i-phase and the W-phase. The addition of 1 at.% of Pb significantly orders the i-phase structure. (C) 2000 Elsevier Science B.V. All rights reserved.