Ternary phase diagram studies in Ti-Zr-Ni alloys

Equilibrium phase formation is reported for ternary Ti-Zr-Ni alloys near th e i-phase-forming composition, for temperature slices between 500 and 700 d egreesC. Selected microstructural results in as-cast and annealed samples a re discussed. Dominant equilibrium phases identified are the C-14-like Lave s 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-tem perature equilibrium phase mixture of the Laves and alpha (Ti/Zr) solid sol ution phases. Lower annealing treatments have not been found to transform t he 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 fo r the i-phase and the W-phase. The addition of 1 at.% of Pb significantly o rders the i-phase structure. (C) 2000 Elsevier Science B.V. All rights rese rved.