Morphology and microstructure of Al-p/SiCp composite powder prepared usinga stone mill

Aluminium based metal matrix composite powder was prepared using a stone mi ll. Elemental powders of pure aluminium and SiC particle reinforcement were milled in a horizontal stone mill at a constant rotation. Two different mi ll gaps were employed to investigate the distribution of SiC particles embe dded in the aluminium matrix. In each case, 1 ton h(-1) of Al-p/SiCp compos ite powder was produced. The shape of the aluminium particles changed from ligamental to spherical and the angular faceted SiC particles became more s pherical in form. Morphological and microstructural observations revealed t hat the advantages of using a stone mill to produce composite powder were t hat it provided well distributed SiC particles and good bonding between mat rix and reinforcement. The mixing mechanism of the stone mill can be descri bed as follows: shear deformation of aluminium particles and embedding of t he SiC into the aluminium flakes, rolling and cold welding of the Al/SiC co mposite flakes to form rolls, and fracture of the composite rolls into sphe rical particles. Hot extrusion improved the distribution of the SiC particl es in the matrix. (C) 2001 IoM Communications Ltd.