Formation of Ni-Al and Ni-Al-X Phases by Mechanical Alloying

Abstract

The Ni-Al phases were synthesized in the composition range 40-85 at. % Ni by mechanical alloying (MA) of elemental component mixtures. MA of Ni-Al powders produces the B2 phase in the range 40 -61 at. % Ni and a solid solution Ni(Al) -in the range 65-85 at. % Ni. Milling of Ni 62.5 Al 37.5 composition results in formation of the B2 and Ni(Al) phases mixture. Formation of a supersaturated solid solution for 65-75 at. % Ni were accompanied by appearance of B2 phase at the intermediate MA stage. Ball milling of Ni and Al powder mixtures of the compositions corresponded to intermetallics NiAl and Ni 3 Al, with a 5 at. % addition of X=Ti, Mo or Nb, where the third element was substituted for Ni (Ni 45 Al 50 X 5 and Ni 70 Al 25 X 5 ), Al (Ni 50 Al 45 X 5 and Ni 75 Al 20 X 5 ) or both (Ni 47.5 Al 47.5 X 5 and Ni 71.25 Al 23.75 X 5 ) was performed. The regularities of influence of the third components on the final structure of the as-milled and annealed alloys were observed. The preferred sublattices for X additions in B2 and L1 2 intermetallic phases were determined.

Phase transformations study on Ni75Al25 and Ni50Al50 during mechanical alloying and sintering

“…For compositions of Ni-25 at.%Al some authors [3,4] reported the formation of Ni(Al) supersaturated solid solution by mechanical alloying, however Pabi et al [5] reported the presence of disordered Ni 3 Al for this composition. Other authors have work on phase transformations of the intermetallic NiAl when adding a third element during milling [9][10][11]. Consolidation of the milled powders by hot pressing and by extrusion has also been carried out [12][13][14][15], the authors obtained high strength at room and elevated temperatures and good compressive ductility.…”