STABILITY OF THE B2 PHASE IN TERNARY TI-AL-X ALLOYS (X=NB, MO, V)

In the first part of this work, the beta (or B2)-stabilizing effective ness was discussed by experimentally determining the temperature depen dence of equilibrium volume fraction of the beta (or B2) phase as well as the variation of the beta-transus temperature as a function of P-a lloying additions. In the second part, the thermal stability of the B2 matrix in three intermetallic compounds (Ti2AlNb, Ti2AlMo and Ti5Al2V ) was studied. Flow stress anomalies were observed in these alloys def ormed in compression as the testing temperature was increased. The tra nsition phases which appear in Ti2AlNb and Ti5Al2V compounds over the 650-850 K temperature range are responsible for these anomalies. Impli cations of such B2 decompositions on the development of this category of alloys are briefly discussed.