THE INFLUENCE OF ALLOYING MODIFICATIONS ON MECHANICAL-PROPERTIES, PHASE-STABILITY, AND FAULT ENERGIES IN CUBIC TITANIUM TRIALUMINIDE-BASED ALLOYS

The cubic titanium trialuminide alloys studied previously show limited ductility and toughness, which can be related to the difficulties of dislocation emission, multiplication and mobility and to the excessive ly high energies of faults associated with the dislocations. The prese nt study examines several new alloys chosen in an attempt to reduce th ese fault energies and thereby improve the mechanical properties. The region of single phase Ll(2) material is unfortunately so limited that only minor changes in composition are possible before second phases f orm and precipitation hardening occurs. Over the range of compositions of the Ll(2) phase evaluated there are generally only small changes i n fault energies. These changes, as well as the changes in dislocation configurations seen, may be rationalized in terms of the instability of the matrix towards the particular second phase forming.