A research on the effect of process parameters on the 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 an Al matrix and B₄C reinforcement particles were prepared by mechanical milling. Powder mixtures were milled for different durations (5, 10, 15, and 20 hours) in a high-energy planetary ball mill. In the milling vials, 10 wt% B₄C particle reinforcements were added to aluminum matrix powders. The average particle size of B₄C and Al powders was 77 μm and 63 μm, respectively. Powder mixtures were compacted as cylindrical samples by uniaxial hot pressing at 30 MPa. Specimens were hot pressed in a nitrogen atmosphere at temperatures of 500°C, 550°C, and 600°C for 15, 30, and 45 minutes. The 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 analyzed using microscopy techniques. Density measurements showed that the compressibility of powders decreased with increasing milling times. Density, hardness, and compressive yield strength values increased with increasing hot pressing temperature and durations.