Squeeze Infiltration Processing and Structural Characteristics of Lightweight Aluminum-Carbon Metal Matrix Composites

Abstract

Natural Graphite flakes are attractive carbon-based reinforcements due to its layered structure providing self-lubrication, thermal properties, cost and ease of machinability. The present study focuses on the processing of high volume fraction graphite-reinforced composites by liquid metal squeeze infiltration technique using various volume fractions of graphite. The interface between the matrix and reinforcement plays a vital role in determining the properties of metal matrix composites (MMC). The presence of oxide layer on the surface of molten metal and the adsorbed contaminant on the reinforcement surface generally leads to non-wetting of the reinforcement with molten metal. To avoid interfacial reactions and improper wetting between Graphite reinforcement and the matrix, the graphite particles were properly surface treated and coated with copper. The graphite particles were coated with copper by cementation technique and characterization has been done. Porous graphite preforms of varying volume fractions and pore densities were prepared through cold pressing followed by vacuum sintering. The sintered porous graphite preforms are infiltrated with liquid aluminum alloy (A356) at 760 °C under squeeze infiltration pressure of 40 MPa. The microstructural characteristics and thermal conductivity measurements were carried out for the infiltrated composites.