Improvement of the mechanical properties in a nanocrystalline NiAl intermetallic alloy with Fe, Ga and Mo additions

Microstructural and mechanical properties characterizations of nanocrystalline Ni-Al+M alloys were carried out. M represents the addition of transition elements such as Fe, Ga and Mo. Mechanical alloying (MA) and densification by hot-pressing techniques were used to produce and consolidate the alloys. The mechanical alloyed powders have a microstructure consisting of nanometer size particles. The main effect of these elements on the microstructure of the NiAl alloy is the refinement of the grain size since this process gives rise to crystallite sizes in the nanometric range. Also, the three minor additional elements form a solid solution with the intermetallic structure of the NiAl. Additions of Mo in the range of 2-6 at.% cause second phase formation of Mo2C. Mechanical properties (hardness, yield stress and strain) were obtained as a function of composition and sintering temperature. The highest hardness value is obtained for the NiAl+2Ga+6Mo (at.%) alloy and always corresponded to the highest densifications (98%) for the sintered samples at 1200 degreesC during 30 min. The Ni-Al alloys with different additions of elements lead to higher deformations than those reported previously. (C) 2002 Published by Elsevier Science B.V.