Aluminium matrix composites reinforced with Al2O3 fibres and graphite
Krzysztof Naplocha, Zdzisław Samsonowicz, Andrzej Janus Politechnika Wrocławska, Instytut Technologii Maszyn i Automatyzacji, ul. Łukasiewicza 3/5, 50-371 Wrocław
Quarterly No. 2, 2005 pages 95-98
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abstract Short alumina fibres with graphite flakes were incorporated into EN-AC AlSi7Mg alloy by the direct squeeze casting process. Porous preforms with about 7÷20 vol.% Al2O3 fibres (Saffil) and 3÷15 vol.% graphite prepared for this composites possess suitable permeability (Fig. 1) and good strength to infiltrate with molten aluminium alloy. Preforms reveal semi-oriented arrangement of fibres and graphite flakes. During production of preforms when high temperature frying process is needed preforms show stable mass and properties. Manufacturing squeeze casting operations at high temperature have not induced chemical reactions between graphite and molten aluminium alloy. Similar conclusions during microscopic observation after thermal treatment (T6) ascertained. Brittle aluminium carbides at the graphite-matrix interface were not observed. Good bonding between matrix and reinforcement were achieved. The composite microstructures exhibit regular arrangement of fibres and slightly worse of graphite flakes (Fig. 2). Composite materials reinforced with low fibre content display better arrangement of graphite flakes (Fig. 3). Interface between matrix and reinforcements is clean, free from any defect and without intermediate area (Fig. 4). Graphite flakes introduced into composite results in a slight reduction of hardness HB (Tab. 1) in relation to composite materials reinforced only with alumina fibres. Graphite flakes form pockets of lubricant agent (Fig. 5) and may consequently improve wear behaviour of this materials. Alumina fibres whereas might restrain intensive abrasion of matrix. Key words: composite, fibre, graphite, aluminium