Effect of spark plasma sintering on the addition of ZrO2 particles to AA7075/B4C composite and its mechanical properties

Abstract

This work investigates microstructural and mechanical properties of hybrid AA7075/B₄C/ZrO₂ composites with varying ZrO₂ reinforcement using spark plasma sintering. The primary objective of the work is to optimize the reinforcement content to achieve a balance between enhanced mechanical properties and microstructural integrity. Composites are characterized by SEM, XRD, and mechanical testing to evaluate tensile strength, compressive strength, hardness, and impact strength. It is shown that 6% ZrO₂ is the best reinforcement content, with tensile and compressive strength peak at 468 and 554 MPa, respectively. Beyond this level, mechanical properties degrade due to the formation of brittle phases, including intermetallic carbides (Al₄C₃), intermetallic compounds (Al₃Zr) and increased porosity, as confirmed by the XRD analysis. Hardness values consistently increase with the higher ZrO₂ content, reaching the maximum hardness of 129 HV at 8% ZrO₂, while the impact strength decreases due to reduced ductility from the intermetallic formation and increased brittleness.