OMEGA PHASE FORMATION IN Ti ALLOYS

The experimental results for three selected ternary alloy systems: Ti-Al-V, Ti-Al-Mo and Ti-Al-Nb show that the formation of ω-phase obeys the electron concentra- tion rule. The valence electron number is N_(Ti)=4(s~2d~2), N_v=5(s~2d~3), N_(Mo)=6(s~1d~5), N_(Nb)=5(s~1p~4) for the transition elements Ti, V, Mo, Nb, respectively, and N_(Al)=3(s~2p~1) for the non-transition element Al. Furthermore, the electronegativities and atomic radii of the al- loying elements will still have some influence upon the ω-phase formation. Sythesizing the valence electron number, electronegativity and atomatic radius of the alloying element, the characteristic value may be fixed at 4.223 in Ti alloy, and which may be expressed as 4.223=∑N_if_i+0.310△x / x_(Ti)+0.551 △r / r_(Ti)