Investigations of the machinability and mechanical properties of Al-Si/SiCp composites produced by powder metallurgy method

In this study, particulate reinforced metal matrix composites (MMCs) were produced by Powder Metallurgy method. Prealloyed Alumix 231 (Al-Si alloy) powder of 63 µm in average size was used as matrix material and SiC particles of 20,1 µm in mean particle size were used as reinforcement material for production of MMCs. Four different specimens containing 0, 5, 10 and 15% weight ratios SiC were produced. Microstructure and some of the mechanical properties (hardness, density and transverse rupture strength) of these specimens were investigated. Microstructural observations showed that the distribution of particles in all of the specimens was relatively homogenous, but porosity occurred in the composite specimens. The highest hardness value was measured as 104 VH5 for the specimen containing 15SiC wt.%. While the highest transverse rupture strength (TRS) was measured on the specimen produced from matrix alloy, the lowest TRS value was obtained on the 15SiC wt.% specimen.The specimens were subjected to machinability tests through turning operation using uncoated cemented carbide, cubic boron nitride and polycrystalline diamond cutting tools. The tests were carried out under dry condition on a computer numerical control (CNC) lathe by using four different cutting speeds, two different feed rates and fixed depth of cut. Machinability of the specimens was investigated in respect of chip formation, tool wear, cutting forces and surface roughness. Especially, tool wear at the nose of WC cutting tool was determined in the high cutting speeds and BUE increased depending on this formation. The cutting forces increased depending on the increased hardness because of weight ratio of SiC. The worst machinability was obtained in the specimen of code 5SiCwt.% in respect of surface roughness. Considering the performance of the cutting tools in terms of surface roughness, to the worst from the best, PCD, CBN and WC were determined. The best surface roughness was obtained by using PCD cutting tool at 0,1 mm/rev and 300 m/min cutting speed with the 15SiC wt.% specimen as ? m 0,45.