Processing, structure and thermal conductivity correlation in carbon fibre reinforced aluminium metal matrix composites

Al matrix composites reinforced with Cu-coated pitch-based carbon fibres (Al/Cu-CFs) were fabricated, using a novel combination of rheocasting and equal channel angular extrusion (ECAE) techniques, in order to exploit the thermal conductivity (K) of the material. Rheocasting allowed the introduction and dispersion of Cu-CFs within the Al3Mg matrix. The subsequent ECAE processing reduced the porosity of the composites from 3 to 0.03% and induced a high degree of fibre alignment within the matrix, although considerable damage to the fibres occurred during this processing step. After 6 ECAE passes, in which the billet orientation remained constant, the composite with the highest degree of fibre alignment show a thermal conductivity (K) improvement of ~20% with respect to the rheocast composite. The improvement is due to porosity reduction, improved fibre alignment and forced intimate contact of clean CF surfaces with the matrix.