Correlation between modulus and yield strength in Ti-25Al-10Nb-3V-1Mo (a/o)

As part of the effort to develop advanced titanium aluminide alloys based on Ti sub 3 Al for aircraft turbine engine components and other high-temperature appications, Lockheed has examined the correlation between modulus and yield strength in Ti-25Al-10Nb-3V-1Mo (a/o). Ultrasonic velocity techniques were used. For alpha sub 2 plus " beta " microstructures, modulus values were directly proportional to yield strength. The correlation was better for heat treatments where no orthorhombic phase was observed. The ultrasonic parameter which is most sensitive to changes in yield strength is the shear velocity. Unlike conventional alloys, where the beta phase has an intrinsically lower modulus than the alpha phase, no such correlation was observed bwetween alpha sub 2 and " beta " in Ti-25Al-10Nb-3V-1Mo.