Hybrid aluminum matrix composites containing carbon nanotubes and zirconium diboride particles: fractography, microstructure and mechanical performance

Hybrid aluminum matrix composites (HAMCs) containing carbon nanotubes (CNTs) and zirconium diboride (ZrB2) particles were prepared via solid-state powder metallurgy route. The constituents of HAMCs were initially ball milled for uniform dispersion, and subsequently composite mixtures were consolidated by cold compaction, which was followed by pressureless sintering. The fractions of nanotubes and ceramic particles in HAMCs were 0.5 wt% and 5.0 wt%, respectively. Individually reinforced composites containing 0.5 wt% MWCNTs and 5.0 wt% ZrB2 particles were also prepared for reference together with pure aluminum. X-ray diffraction identified the crystalline phases while optical and scanning electron microscopy revealed uniform dispersion of reinforcements without their agglomeration. Mechanical characterization showed a significant rise in the properties of HAMCs over unreinforced aluminum and composites containing individual reinforcements. The improvements of similar to 26%, similar to 34% and similar to 19% in hardness, compressive strength and flexural strength were observed in comparison with pure aluminum, respectively. The examination of fractured surfaces revealed the strengthening mechanisms responsible for the improvement in mechanical performance of HAMCs.