Abstract
Aluminum metal matrix composite AMMCs reinforced with ceramic particles have a wide acceptance in engineering application due to their properties, but continuing problem with these materials is the difficulty of their machining due to hardness and abrasive nature of the reinforcing ceramic particles. The present work is aimed at studying the preparing of hybrid AMMC reinforced with both SiC particles and particles of graphite that have a lubricant effect. Stir casting technique was used to prepare samples with 6wt% SiC, and a hybrid sample with 6wt% SiC and 6wt% graphite. The effect of such reinforcements was investigated. The investigation included: hardness, compressive strength, required cutting force, surface roughness, as well as microscopic analysis, SEM-EDS analysis and also XRD analysis. Cemented carbide turning tool (P10) was used in all machining experiments with wide ranges of machining conditions to measure the surface roughness, and the cutting force.
The results showed that an improvement of (184.8%) in macrohardness and (85%) in compressive strength had been achieved by reinforcing with 6wt% SiC, while these properties were improved by (33%) and (23%) by reinforcing with both SiC and graphite. The results of machining experiments showed that reinforcing with SiCp alone caused the surface roughness and the main cutting force to be increased by (32-80%) and (50.5–100%) respectively in comparison with the base matrix. In hybrid composite graphite reduces the effect of SiCp on the surface finish, so as the roughness of the machined hybrid sample was increased only (22.9 - 70.4%) in comparison with that for base matrix, while the main cutting force was increased only (42 - 66%).