Effect of MA on microstructure and synthesis path of in-situ TiC reinforced Fe–28at.% Al intermetallic composites

An in-situ composite consisting of titanium carbide and iron aluminide was synthesized by mechanical alloying of elemental powders and pulse discharge sintering. The microstructure and synthesis path of in-situ TiC reinforced Fe–28at.% Al composite were examined as a function of milling time and heat treatment temperature. Mechanical alloying of the elemental powders promoted bcc solid solution formation, and the solid solution completed at milling of 400 h. During sintering Fe3Al and TiC precipitated from the supersaturated Fe solid solution containing Al, Ti and C. Microstructure of the sintered body made of powder milled for 200 h consists of three regions, that is, large TiC particles of about 5 μm in size, Fe3Al matrix with TiC particles of submicron size and particle-free Fe3Al region. For the sintered body after milling of 400 h, however, the large TiC particles disappeared due to the complete solid solution during mechanical alloying. Sintering of the powders milled for the period shorter than 50 h formed intermediate phases, such as Al5Fe2, Al3Ti and Fe3AlCx, by heat treatment up to 1273 K, while that of the powder milled for 400 h showed direct precipitation of Fe3Al and TiC from the Fe solid solution.