Processing and mechanical behaviour of TiAl/NiAl intermetallic composites produced by cryogenic mechanical alloying

Cryogenic mechanical alloying of intermetallic powders has been used to produce TiAl/NiAl intermetallic composites. High-energy milling of prealloyed titanium aluminide and nickel aluminide powders at liquid nitrogen temperature results in the stable non-equilibrium mixtures with a fine grain size. Subsequent consolidation by uniaxial hot pressing produces unusual intermetallic composites. Powders and consolidated materials are characterised using microscopy and X-ray diffraction (XRD). Mechanical properties are evaluated by small punch testing and through microindentation measurement. It has been found that no new phase is formed during milling of intermetallic mixtures. Consolidated powders have exhibited exceptionally high hardness. The low fracture toughness of consolidated materials is attributed to the formation of ternary phases during consolidation.