Preparation And Characterization Of Aluminum Matrix Composite By Powder Metallurgy

Particles reinforced aluminum matrix composites have been widely used instructural materials due to their high ratios of stiffness-quality and strength-quality.It makes them excellent structural light materials that they show good friction,thermal conductivity and low coefficient of thermal expansion, which makes itpossible to apply particles reinforced aluminum matrix composites to aircrafts andtransportation. Carbon nanotubes due to their good mechanical properties andperfect structure have been considered as ideal reinforcements of light structuralcomposites. It is revealed that multi-wall carbon nanotubes’ Young modulus reaches1.8TPa and tensile strength150GPa, while the density only is1.8g/cm3. Carbonnanotube reinforced aluminum matrix composites have been extensively appliedbecause of the properties of lightness, high strength and good friction. Thegraphenes due to their excellent properties is being paid attention to recently andapplied to aluminum matrix composites.In this research three kind of reinforcements including nano-SiC particles,multi-wall carbon nanotubes, single-wall carbon nanotubes and graphenes wereadded to aluminum matrix to prepare the composites by powder metallurgy routeconsisting of ball milling, cold compaction, sintering, hot pressing and hotextrusion, in which pressure sintering was divided to pressureless sintering and hotpressing. Universal testing machine, Brinell hardness tester, Friction-abrasiontesting machine, Coefficient of thermal expansion tester, Electrochemicalworkstation, XRD and SEM were respectively used to characterize the propertiesof composites including tensile strength, brinell hardness, friction, coefficient ofthermal expansion, corrosion resistance, the phases and fracture morphology.It is revealed that when the addition of nano-SiC particles is5wt%the tensilestrength is215MPa, which increases by110%compared with pure aluminum.However, when the addition of alpha-SiC particles is10wt%, the tensile strengthonly reaches160MPa. With the increasing addition of carbon nanotubes (0-2wt%),the hardness increases while the tensile strength increases firstly and decreases.When the addition is1.5wt%, the tensile strength reaches380MPa, the hardnessand tensile strength respectively increases by433%and245%compared with purealuminum. However, the coefficient of friction and wear amount decrease. When the addition is2wt%, the two properties respectively decrease by63%and14%.The addition of carbon nanotubes has no effect on the coefficient of thermalexpansion. When the addition of the graphenes is2wt%, the tensile strength ofcomposites reaches310MPa, increasing by182%compared with pure aluminum. Itis concluded that carbon nanotube is one of the best candidates for aluminummatrix composites among the material which we chose.