Morphology and microstructure of Alp/SiCp composite powder prepared using a stone mill

Abstract

Aluminium based metal matrix composite powder was prepared using a stone mill. Elemental powders of pure aluminium and SiC particle reinforcement were milled in a horizontal stone mill at a constant rotation. Two different mill gaps were employed to investigate the distribution of SiC particles embedded in the aluminium matrix. In each case, 1 ton h-1 of Alp/SiCp composite powder was produced. The shape of the aluminium particles changed from ligamental to spherical and the angular faceted SiC particles became more spherical in form. Morphological and microstructural observations revealed that the advantages of using a stone mill to produce composite powder were that it provided well distributed SiC particles and good bonding between matrix and reinforcement. The mixing mechanism of the stone mill can be described as follows: shear deformation of aluminium particles and embedding of the SiC into the aluminium flakes, rolling and cold welding of the Al/SiC composite flakes to form rolls, and fracture of the composite rolls into spherical particles. Hot extrusion improved the distribution of the SiC particles in the matrix.