Preform-Based Production of Al2O3-Reinforced Aluminium Matrix Composites by Using Various Modification Techniques

Abstract

Metal matrix composites have a wide range of applications due to their lightweight, high strength and high wear resistance. In this study, Al2O3-reinforced AA7075 matrix composites were produced by using liquid metal infiltration method in two stages. In the first stage of the production, preforms were manufactured by using Al2O3 particles and different binders. Some of the preforms were sintered and some were not sintered. In the second step, liquid metal infiltration was performed on both sintered and not sintered samples. Some preforms were preheated before the infiltration and some were directly subjected to the liquid metal infiltration. The casting process was carried out in two different ways: (1) pouring the molten metal into the fired mould and (2) in situ melting of the metal during the mould firing. Fabricated composites were characterized by XRD, light metal microscopy, SEM, EDS, Brinell hardness and ball-on-disc type wear tests. When the microstructural, mechanical and tribological properties were taken into account, preheating and sintering preforms before casting were determined as performing best with the hardness of similar to 150 HB and the wear rate of 1.1 x 10(-4) mm(3)/(N m), whereas the in situ melting caused decrease in the mechanical strength and wear resistance because of excessive oxidation.