The mechanical properties and microstructure of aluminum matrix composites containing of zircon (10, 15 and 20 wt.%) as a reinforcement particles and cobalt additive (1, 1.5 and 2 wt.%) were investigated. The aluminum matrix composites were prepared by powder metallurgy technique and sintered in both conventional and microwave furnaces at temperatures higher than the melting point of aluminum. The results revealed that the density and mechanical strength of aluminum were increased by introducing zircon and cobalt particles. The maximum strength was obtained by adding 10 wt.% zircon sintered in microwave furnace at 950ºC. The phase analysis and scanning electron microscopy of sintered composites were examined and found some interesting data about intermetallic compounds.

Aluminum-15 wt. % zircon metal matrix composite was fabricated using spark plasma sintering method at the temperature of 450°C and holding time of 4 min. The bending strength of 284±21 MPa and microhardness of 171±14 Vickers were determined for produced composite. XRD investigations proved that almost no decomposition of zircon particles as reinforcement occurred. SEM studies revealed the homogenous dispersion of reinforcement particles in the aluminum matrix.

Abstract Microwave assisted rapid sintering was carried out to fabricate aluminum-ZrB2 metal matrix composites containing 1 wt% cobalt and 10, 15 and 20 wt% ZrB2 as the reinforcements at temperatures of 600, 700 and 800°C. The results showed that the highest values of density and bending strength (97% of theoretical density and 240 MPa, respectively) were obtained in a composite containing 15 wt% ZrB2 and 1 wt% Co sintered at 600°C. Furthermore, the optimum values of compressive strength and hardness (350 MPa and 63 Vickers, respectively) were measured for a composite containing 20 wt% ZrB2 sintered at 600°C. At all sintering temperatures, XRD analysis revealed ZrB2 and aluminum as the only crystalline phases. Microstructure investigations demonstrated a homogeneous distribution of ZrB2 particles in the aluminum matrix.

Metal matrix composites of Al-WC (10, 15 and 20 wt%) were prepared by microwave (without holding) and conventional sintering (held for 1 hour) processes at various temperatures between 650-950 °C. The results indicated that the highest density of conventional and microwave sintering corresponds to 97.4 ± 1.2% and 98.6 ± 0.8 of theoretical density, respectively; The highest bending strength of conventional and microwave sintered samples were 223 ± 12 and 256 ± 12 MPa, respectively. XRD patterns showed the decomposition of WC particles and formation of Al5W and Al12W interfacial reaction product phases in both processes. SEM studies showed that WC reinforcement particles were more likely to be agglomerated in microwave compared to conventional sintering process.