Microstructure and strength of binary and tantalum alloyed two-phase Nbss/Nb3Al base alloys

Niobium aluminide (Nb3Al) base intermetallic compounds are potential candidates for applications at temperatures above the operating temperatures of currently used superalloys, provided their low-temperature ductility and fracture toughness and high-temperature oxidation resistance are improved. Two-phase (Nbss/Nb3Al) materials with different volume fractions depending on the aluminium content were prepared by ingot metallurgy followed by isothermal forging and heat treatment. The addition of tantalum (about 10 mol%) has no influence on the phase content, volume fraction and grain size. The compressive strength of both the binary and ternary alloys investigated depends strongly on the aluminium content. Increasing the volume fraction of Nbss phase decreases the strength at all temperatures tested. The addition of tantalum improves the high-temperature strength of Nbss/Nb3Al alloys.