الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Composites attract interest due to their high mechanical and wear properties. The effect of Al2O3 content and compaction temperature on physical, mechanical and tribology properties of Al–Al2O3 nano-composites (alumina is coated with Cu) is studied. Homogeneity of Al matrix reinforced with Al2O3 nanoparticles coated with Cu (0, 5, 10 and 15wt. % Al2O3) prepared by powder metallurgy is improved. Alumina particles surface is activated with 10wt. % Ag, then coated with Cu by electroless deposition. Appropriate amounts of Al and Al2O3 (coated with Cu) are well mixed in a ball mill (4:1 balls to powder ratio) for 6 h. The mixture is sintered at 400, 500 and 600 o C under 700 MPa uniaxial pressure for 45 min in argon atmosphere. Increasing Al2O3 content to 10wt. % improves hardness and wear properties of samples compacted at 400ᵒC. Further increase to 15wt. %, decreases the properties, due to agglomeration of Al2O3 and reduction of relative density. Also, hardness, compressive strength, wear resistance and thermal expansion, increase with increasing Al2O3 content for samples compacted at 500 and 600 o C. This is attributed to grain refinement, hard particulates homogeneous distribution, dislocations generation, as well as mismatch of coefficients of thermal expansion of the matrix and reinforcement.
Hot compaction temperature highly affects the structural, mechanical, physical and wear properties. Compaction at 400, 500 and 600oC leads to grain size of 116, 78 and 49 nm, respectively. Hot compaction increases the relative density of nanocomposite, which increases hardness, compressive strength, and thermal expansion as well as wear resistance. However, densification, thermal conductivity and ductility of the Al MMCs deteriorate significantly at higher Al2O3 nanoparticles (coated with Cu) contents. Electroless deposition of Cu on Al2O3 nanoparticles followed by ball milling and compaction at 700 MPa is efficient to produce Al–Al2O3 nanocomposite with high Al2O3 content.