Relationship of Structure to Strength in Titanium Alloys.
Final rept. 1 Jul 66-30 Jun 69,
MASSACHUSETTS INST OF TECH CAMBRIDGE
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The formation of the omega and alpha phases on quenching and aging and of martensite under an applied stress has been studied in binary, beta isomorphous titanium alloys containing molybdenum, niobium and vanadium. Thermodynamic calculations using the regular solution approximation reveal that the beta phase of niobium-and vanadium-containing alloys exhibit a tendency for phase separation while a tendency for ordering exists in titanium-molybdenum. Compositional fluctuations in the beta phase can lead to an increase in the driving force for alpha phase formation in titanium-vanadium. Hexagonal close-packed, stress-induced martensite forms in molybdenum and vanadium alloys, as expected from thermodynamic considerations. Furthermore, the influence of omega and alpha precipitation on the deformation behavior at normal strain rates has been studied. The apparent embrittling effect of omega is found to be associated with the large volume fraction and fine particle size of nondeformable precipitates. Prior omega formation is shown to influence the dispersion of alpha precipitates and to yield good tensile properties. Under high strain conditions, greatest strengthening is obtained after simultaneous deformation and transformation in metastable beta alloys and alpha phase titanium where pressure-induced transformations are found to occur. Author
- Properties of Metals and Alloys
- Fabrication Metallurgy