Effect of mechanical alloying process on mechanical properties of α-Si3N4 reinforced aluminum-based composite materials

In this study, Al–α-Si3N4 metal matrix composite (MMCs) materials were produced by using powder metallurgy technique. To prepare mixture of Al and α-Si3N4 powders two different methods were used by milling for 5 h in a ball mill with alumina balls and mechanically alloying for 5 h in a high-energy attritor mill. Then mixed powders were compacted under 1000 MPa pressure to produce standard transverse rupture block specimens with dimension of 6.35 × 12.70 × 31.70 mm. Compacted samples were then sintered at 620; 640; 660; and 680 °C for 2 h under argon atmosphere in a tube furnace. The mechanical properties of the composite specimens were determined by measuring the density, hardness and transverse rupture strength values. Using optical and scanning electron microscopy (SEM) were also observed microstructures of the composites. The results showed that, more homogenous dispersion of α-Si3N4 powders were obtained in Al matrix using the mechanical alloying technique according to classical mixing method. Especially, as a result of homogenous dispersion each other of Al and α-Si3N4 powders high hardness and transverse repute strength values were obtained from these samples.