MICROSTRUCTURAL DEVELOPMENT OF A GAS-ATOMIZED AND HOT-PRESSED SUPER-ALPHA(2) ALLOY

A variety of heat treatments have been employed to explore the microst ructure in Ti-25Al-10Nb-3V-1Mo alloy prepared by gas atomization and h ot pressing. These treatments include quenching by oil cooling and wat er cooling and aging at temperatures between 530 degrees C and 950 deg rees C. Quenching transformations from the beta-phase field include th e formation of O phase in oil quenching and beta (disordered) + O phas e in water quenching. The metastable beta phase decomposes into O + '' omega'', O, or alpha(2) + beta(0)/B2 phase when the as-quenched alloy is aged at various temperatures. By comparing the selection area diffr action patterns, it has been found that the ordered omega phase in the alloy studied in this article is distinct in structure to the ''omega type'' (P3m1) and B8(2) phase which are formed in the parent matrix o f the ordered beta(B2,D0(3)) phases. It has also been shown by X-ray d iffraction (XRD) analyses that the lattice parameters of the as-aged O phase do not remain constant in the alloy at various temperatures.