Improvement of thermophysical and machinability properties of Al matrix composites with CFs-D hybrid reinforcement

The carbon fibers-diamond (50 vol%)/ Al composite (CFs-D/Al) was successfully designed and fabricated using gas pressure infiltration. By comparing it to the carbon fiber/Al composite (CFs/Al), a dual reinforcement structure with both soft and hard materials was formed, resulting in improved anisotropy. This improvement can be attributed to the high hardness of diamond (D), which bears most of the pressure during infiltration. The thermal conductivity (TC) of the CFs-D/Al in the XY plane and Z direction were measured to be 249.97 W center dot m- 1 center dot K- 1 and 225.81 W center dot m- 1 center dot K- 1, respectively. These values represent a 27.24% and 133.2% increase in TC compared to CFs/Al. The improved anisotropy, excellent TC of diamond, high density, and good interface are the main factors contributing to this enhancement in thermal conductivity. Additionally, CFs-D/Al demonstrated acceptable coefficients of thermal expansion (CTEs) of 7.26 x 10-6 K-1 (in the XY plane) and 10.04 x 10-6 K-1 (along the Z direction). This is mainly attributed to the low CTE of carbon fibers and diamond, as well as the presence of good interfacial pinning and residual stress in the composite. Furthermore, the addition of carbon fibers greatly reduced the wear of cutting tools compared to D/Al. The surface roughness of the CFs-D/Al after machining was measured to be 5.939 mu m, which is 51.86% and 70.97% lower than that of CFs/Al and D/Al, respectively. This reduction in surface roughness can be attributed to the lubricating effect of CFs and the ability of D to prevent peel pits under the adhesive wear mechanism. This research utilized the design concept of combining the advantages of different reinforcements to surpass the limitations of using a single reinforcement for heat dissipation purposes.