AMORPHIZATION IN THE AL-C SYSTEM BY MECHANICAL ALLOYING

Mechanical alloying of a powder mixture of elemental Al and graphite h as 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 prod uct. Further milling leads to destabilization of Al4C3. It is proposed that destabilization of Al4C3 is induced by the accumulated defects a nd 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 s olution with a carbon content up to 23 at%. Whereas an amorphous phase is formed in the composition range of 28-50 at% C. (C) 1997 Elsevier Science S.A.