Fabrication method, microstructural characteristics, and hardness behavior of an interpenetrating phases hybrid aluminum/alumina-nanodiamond composite

In the present work, the addition effects of nanodiamond (ND) on the microstructure and hardness behavior of interpenetrating phases hybrid Al/Al۲O۳ metal matrix composites were investigated. The fabrication of the composites was done via a two-step process. In the first step, hybrid Al۲O۳-ND preforms were prepared, and then molten pure Al alloy was infiltrated into the preforms. The preforms were fabricated by the replica method using a polyurethane foam and an Al۲O۳-ND slurry with various ND contents (۰, ۱, ۳, and ۱۰ vol%). The preforms were sintered at ۱۵۰۰ °C for ۴ h under argon gas protection. Finally, the composites were fabricated by Al melt infiltration into the preforms via the squeeze casting method. The microstructure of the fabricated composites was analyzed using optical and scanning electron microscopes. The hardness of the composites was measured using a Vickers hardness tester. The results of the microstructural evaluations demonstrated a good distribution of ND in the preform. By increasing the ND content from ۰ to ۱۰ vol%, the matrix average grain size decreased from ۱۴۳ μm to ۷۶ μm. The results of the Vickers hardness test showed that increasing the volume percentage of ND increased the composite hardness to ۲۶۳.۸ Vickers at ۱۰ vol%. The two main strengthening mechanisms for these composites are the Orowwn mechanism (volume fraction of ND particles) and the Hal-Petch mechanism (grain size), which affect the hardness behavior.

Keywords:

Aluminum-matrix composite , Interpenetrating phases , Nanodiamond , Microstructure , Hardness