BALL-MILLING OF ELEMENTAL POWDERS - COMPOUND FORMATION AND OR AMORPHIZATION

Mechanical alloying of elemental powders has been carried out by ball-milling in a number of systems containing boron and silicon with chromium and niobium. Detailed analysis of the milled powders has been performed by X-ray diffraction and electron microscopy as a function of milling time. Compound formation occurs in both chromium and niobium silicides but only in niobium containing borides, whilst chromium containing borides never form up to 80 h milling time. In all cases, partial amorphization was observed after 60 h milling indicating that the amorphization process is independent of the different paths followed by the different systems. Amorphization is related to the degree of atomic disorder produced during the milling process.