Phase transformations in niobium base alloys, quenched from liquid state

Phase transformations in strongly oxygen oversaturated solid solutions on niobium base in the field of temperatures of suboxide existence and amorphous alloy constituent crystallization are studied. It is shown that fast quenching from liquid state of preeutectic niobium alloys with oxygen as well as niobium alloys with oxygen doped by titanium contributes to formation of amorphous-crystalline structure. A considerable oxygen enrichment of crystalline as well as amorphous components occurs. Oxygen solubility in niobium increases up to 12-13 at.%. Amorphous phase crystallization is realized at 673-773 K annealing temperatures with formation of NbO and Nb2O5 oxides. The decomposition of oversaturated solid solutions in the temperature range from room to 673 K is followed by formation of NbOsub(x) metastable phase. Phase transformations in niobium alloys with oxygen fast quenched from liquid state at annealings above 973 K occur in conformity with an equilibrium phase diagram