Synthesis and Characterization of Aluminum–Zirconium Intermetallic Composites

Abstract

The search for composite materials comes from a necessity of improving properties of conventional materials. The reaction synthesis process frequently gives products with some level of porosity that may be improved through the use of hot pressing routes. The combination of aluminum and zirconia in controlled conditions has led to a metal matrix composite with a dispersion of intermetallics, especially Al₃Zr. Temperature, pressure, and chemical composition were the main parameters varied during the production of the samples. The experimental procedures consisted initially of the mixing and homogenization of the powders in three proportions (5, 10, and 20 in zirconia wt. %). The powders were pressed for the production of green bodies, cylinders of 9 × 9 mm, with the application of three pressures (150, 250, and 300 MPa). Synthesis was carried out in a tubular furnace (1073, 1173, and 1273 K) using a helium atmosphere. Reactive hot pressing was carried out in a MTS machine. The densification process in the simultaneous hot pressing was observed with the use of mercury picnometry to measure the densities and confirmed with the help of an image analyzer. The temperatures were monitored by a thermocouple connected to an A/D interface. Determination of Vickers microhardness was carried out in the aluminum matrix and in the intermetallic particles; hardness was determined in all samples. The identification of the phases was obtained utilizing XRD, optical, and SEM microscopy.