Phase formation in mechanically alloyed Nb-Al powders

Hellstern, E.; Schultz, L.; Bormann, R.; Lee, D.
October 1988
Applied Physics Letters;10/10/1988, Vol. 53 Issue 15, p1399
Academic Journal
Nb-Al alloys have been prepared by mechanical alloying of elemental crystalline powders and investigated with x-ray diffraction and transmission electron microscopy. Crystalline equilibrium phases form for Al-rich alloys. Amorphous phase formation is observed for the Nb50Al50 composition. Mechanically alloyed powders with more than 70 at. % Nb exhibit the metastable bcc (A2) solid solution which transforms after thermal annealing into the A15 phase. Formation of the different phases can be understood by considering the free-energy curves of the amorphous and bcc phases as calculated from the phase diagram and additional thermodynamic data.


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