Mechanical alloying synthesis and structural characterization of ternary Ni-Al-Fe alloys

Ternary Ni-Al-Fe alloys with different Fe additions have been synthesized by mechanical alloying of elemental powder mixtures. The effects of Fe-substitution for Al in an equi-atomic NiAl alloy on the mechanical alloying process and on the final Ni-Al-Fe alloys were investigated experimentally. Lower Fe additions have been found to prolong the milling time prior to explosive formation of the NiAl(Fe) compound, while ≥ 15 at % Fe addition has been found not only to eliminate the explosive reaction during milling but also to produce a Ni-based supersaturated solid solution (the 15 at % Fe addition results in the formation of an amorphous-like phase). The addition of Fe improves the plastic deformation ability of the alloys and hinders the tendency of fracture during milling, resulting in the formation of larger alloy particles. Upon heating, the as-milled samples with lower Fe addition remain as NiAl(Fe) compound, whereas the Ni-based supersaturated solid solutions decompose into a mixture of compounds of β-(Ni, Fe) (Al, Fe) + γ′-(Ni, Fe)3Al. It is suggested that the ternary addition into the binary intermetallic compound might be a possible route to improve ductility by forming the dual phase of β + γ′.