Synthesis and characterisation of quasicrystalline Al based composites

Al matrix composites reinforced by Al-Cu-Fe quasicrystalline (QC) phase particles were produced from a mixture of Al and QC powders using electrical current heating and conventional sintering. A combination of X-ray diffractrometry, transmission and scanning electron microscopy was used to characterise the microstructure of consolidated specimens. The metallic bonding of the Al matrix and particles was improved by higher temperature sintering or electrical current heating. However, the dissolution of QC particles into the Al matrix was inevitable during heating and resulted in the formation of omega and/or beta phases. The dissolution of QC particles was effectively reduced using prealloyed Al powder containing 2 at. -% Cu. This had led to an increase in microhardness from 96 to 139 HV for specimens using pure Al to prealloyed Al powders. A homogeneous distribution of QC particles within the Al matrix could be achieved by mechanical milling followed by consolidation.