Amorphization in the Al---C system by mechanical alloying

Mechanical alloying of a powder mixture of elemental Al and graphite has been performed in a high-energy ball mill. The structural evolution has been characterized by X-ray diffraction and transmission electron microscopy. The carbide Al₄C₃ is first formed as an intermediate product. Further milling leads to destabilization of Al₄C₃. It is proposed that destabilization of Al₄C₃ is induced by the accumulated defects and the high pressure due to collision of the balls. Balling milling of the elemental Al---C powder mixture finally results in a f.c.c. solid solution with a carbon content up to 23 at%. Whereas an amorphous phase is formed in the composition range of 28–50 at% C.