The formation of Al-Ni compounds by ball-milling of elemental powders has been investigated by means of in situ thermal analysis, x-ray diffraction, and scanning electron microscopy. The results show that AlNi forms in an explosive, exothermic reaction, driven by the large heat of compound formation. The mechanism discovered is suggested to explain the mechanical alloying of other systems.

• Received 18 August 1989

DOI:https://doi.org/10.1103/PhysRevLett.64.487