Synthesis of FeAl-TiN nanocomposite by mechanical alloying of Al-Fe-Ti powder mixture under nitrogen atmosphere

Mechanical alloying process has attracted much attention as a method to synthesize alloys through not only a solid-solid reaction, but also a solid-gas reaction. In the present work, the mechanical alloying process was used for synthesizing a FeAl-TiN nanocomposite. A powder mixture of Al-Fe-Ti (equal proportions) was milled in a high energy ball mill under a nitrogen atmosphere. The phase evolution occurring in the powder during the milling was monitored by the X-ray diffraction method. Transmission electron microscopy was used for examining the microstructure of the milling product. The results obtained show that the process leads first to amorphisation of the material and then to transformation of the amorphous phase into disordered FeAl phase and TiN nitride, both nanocrystalline. In order to check the thermal stability of the product phases, the milled powder was subjected to heat treatment and then examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). No phase changes, except an ordering of the FeAl phase, were found in the XRD pattern of the powder after the heat treatment. It was observed that for the heat treated powder, all the peaks in the XRD pattern were sharper than those obtained for the untreated powder. This effect is due certainly to a stress release and some crystallite growth. The latter was confirmed by TEM observations.