Microstructure and mechanical properties of aluminum matrix composites with different volume fractions of surface-oxidized nanodiamonds

Nanodiamonds (NDs) have the characteristics of both diamonds and nanomaterials. However, it is difficult to disperse NDs, and this is why there is less research regarding NDs in the field of aluminum matrix composites. In the present work, NDs were modified via surface oxidation, and ND/Al matrix composites were successfully prepared via mechanical ball milling and vacuum sintering. The effects of different volume fraction of NDs (1%, 3%, 5%, 7%) after surface oxidation on the ND/Al matrix composite were analyzed using a metallographic microscope, scanning electron microscope, infrared spectrometer, X-ray diffractometer, microhardness tester, and universal testing machine. The results show that the optimal temperature of surface oxidation treatment is 673 K, which effectively purifies the surface of ND and introduces appropriate C=O functional groups. NDs are uniformly distributed in the aluminum matrix, and no harmful Al4C3 phase is formed. With an increase in the volume fraction of NDs, the grain size of the matrix first decreases and then increases, and the ultimate compressive strength first increases and then decreases. The volume fraction of ND with better comprehensive performance is 3% and the yield strength increased by 19%.