Effect of zirconium diboride addition in zirconium dioxide reinforced aluminum-based composite fabricated by microwave sintering technique

In the present investigation, zirconium dioxide (ZrO₂) and zirconium diboride (ZrB₂) have been used in the development of an aluminum-based composite. A microwave sintering technique was employed for the processing of the composite. The aluminum-based composite was developed with the constant 5 wt.% of ZrO₂. The weight percent of ZrB₂ increased from 2.5% to 7.5%. Uniform distribution of the reinforcement particles was observed for the composition Al–5 wt.% ZrO₂–2.5 wt.% ZrB₂ composite and Al–5 wt.% ZrO₂–5 wt.% ZrB₂ composite. The relative density of Al–5 wt.% ZrO₂–5 wt.% ZrB₂ composite was found to be 0.9874. The percent porosity of the Al–5 wt.% ZrO₂–5 wt.% ZrB₂ was 1.259%. Results showed that hardness, compressive strength, % tensile strength, and fatigue strength (at 1 × 10⁷ cycles) were improved by about 74.28%, 18.18%, 58.77%, and 60.77%, respectively. XRD of the Al/ZrO₂/ZrB₂ composite showed the presence of Al, ZrO₂, ZrB₂, MgAl₂O₄, and Al₂Cu phases. The number of grains per square inch for composition Al–5 wt.% ZrO₂–5 wt.% ZrB₂ composite was found to be 989.11. This result showed that a finer grain structure has been obtained after the solidification of Al–5 wt.% ZrO₂–5 wt.% ZrB₂ composite. The fracture surface of the Al–5 wt.% ZrO₂–5 wt.% ZrB₂ composite was composed of a dendrite structure with micro-porosities. Dimples were also not observed from the tensile fracture surface morphology of the composite.