Investigations of the producibility and machinability of metal matrix composites reinforced with MgO by infiltration method

Composite materials are the engineering materials have a rapidly expanding using field and have very different production methods. Within the scope of this work, a kind of MMC which has a common field of usage is manufactured and its machinability inspected by applying the vacuum infiltration method. The study has been done at two step; the first step is producing of MMC materials and the second step is investigation of machinability of materials that contains different reinforcement rates.On production of MMC, aluminum powder in the size of 295 µm approximately and purity of 99,7 % is used as the matrix material, and so are the magnesium particles (MgO) in the size of 149 µm approximately as the reinforcement element are used. 3 different composite samples contains 5 %, 10 %, 15 % MgO in weight have been manufactured. The affects of production parameters on the infiltration distance, composite micro-structure, breaking strengths and hardness have been determined. It has been found out that an increase in the infiltration temperature and period, reinforcement grain size, vacuum value and liquid matrix?s Mg content raise the distance of infiltration, and an increase in the reinforcement volume rate vice versa. The sample with 5 % MgO reinforcement has the highest hardness value and cross-breaking strength.The produced MMC samples are subjected to machining experiments by turning process using sementite carbide (SC) and coated cubic boron nitride (CBC) cutting tools. Machining experiments have been carried out using four different cutting speed (150, 200, 250, 300 m/min), three feeding rate (0,075 - 0,15 ? 0,225 min/rev) at constant cutting depth and dry cutting conditions. The machinability features of samples are investigated in terms of cutting forces and surface roughness.On the evaluation made in the respect of cutting forces, it is understood that ?the more the cutting speed is, the lower the cutting force gets? and ?the more the advance is , the more the cutting force gets?. While the best results in the respect of cutting forces are obtained from the samples in the rate of 10 % reinforcement ? volume (R-V), the best results are obtained from the carbide (C) cutting tools for the samples in the rates of 5% and 10 % R-V. For the samples in the rate 15 % MgO reinforcement , the performance of the C cutting tools, by which we obtain the best results at the low advance rates, goes into an abrasion period and decreases by an increase in the chip load and the effect of the hard phase. While surface finishes tend to recover by an increase in the cutting speed, the surface roughness values tend to rise by an increase in the advance. In a similar way to the cutting forces while the best results for the samples in the rate of %5 and 10 % MgO reinforcement are obtained from the C cutting tools, the better results for the higher rate of T-H are obtained from the CBN C tools at the high advance rates. On the inspections of the SEM on the tools, it is observed that built up edge (BUE) has a tendency to build up at the cutting rate of 150 m/min., having an adverse affect upon the cutting forces and the surface finish.Key Words: Composites, metal matrix composite, ınfiltration, aluminium,mgo, machinability, cutting forces, surface roughness