Synthesis and structural characterization of nanocrystalline (Ni, Fe)3Al intermetallic compound prepared by mechanical alloying

Synthesis of (Ni, Fe)3Al intermetallic compound by mechanical alloying (MA) of Ni, Fe and Al elemental powder mixtures with composition Ni50Fe25Al25 was successfully investigated. The effects of Fe-substitution in Ni3Al alloy on mechanical alloying process and on the final products were investigated. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry, scanning electron microscopy and microhardness measurements. At the early stages, mechanical alloying resulted in a Ni (Al, Fe) solid solution with a layered nanocrystalline structure consisting of cold welded Ni, Al and Fe layers. By continued milling, this structure transformed to the disordered (Ni, Fe)3Al intermetallic compound which increased the degree of L12 ordering upon heating. In comparison to Ni–Al system, Ni (Al, Fe) solid solution formed at longer milling times. Meanwhile, the substitution of Fe in Ni3Al alloy delayed the formation of Ni (Al, Fe) solid solution and (Ni, Fe)3Al intermetallic compound. The microhardness for (Ni, Fe)3Al phase produced after 80 h milling was measured to be about 1170HV which is due to formation of nanocrystalline (Ni, Fe)3Al intermetallic compound.