A research on effect of process parameters on mechanical properties of B4C reinforced aluminum matrix composites fabricated by mechanical milling and hot press sintering route

The aim of this study is to investigate the effect of mechanical milling and hot pressing process parameters on the density and strength of Al/B4C composites. For this research, powder mixtures consisting of Al matrix and B4C reinforcement particles were prepared by mechanical milling. Powder mixtures were milled for different times (5, 10, 15 and 20 hours) in a high energy planetary ball mill. In the milling vials, 10wt% B4C particle reinforcements were added to aluminum matrix powders. Average particle size of B4C and Al powders were 77μm and 63μm respectively. Powder mixtures were compacted as cylindrical samples by uniaxial hot pressing at 30 MPa. Specimens were hot pressed in nitrogen atmosphere at temperatures of 500-550-600 °C for 15-30- 45 minutes. Effects of milling and hot pressing variables on microstructure and mechanical properties were investigated by means of density and hardness measurements and compression tests. Microstructures of powders and compacts were investigated by microscopy techniques. Density measurements showed that compressibility of powders decreased with increasing milling times. Density, hardness and compressive yield strength values were increased with increasing hot pressing temperature and durations.