Preparation and investigation of Al-4 wt% B4C nanocomposite powders using mechanical milling

Boron carbide nanoparticles were produced using commercially available boron carbide powder (0.8 mu m). Mechanical milling was used to synthesize Al nanostructured powder in a planetary ball-mill under argon atmosphere up to 20 h. The same process was applied for Al-4 wt% B4C nanocomposite powders to explore the role of nanosize reinforcements on mechanical milling stages. Scanning electron microscopy (SEM) analysis as well as apparent density measurements were used to optimize the milling time needed for completion of the mechanical milling process. The results show that the addition of boron carbide particles accelerate the milling process, leading to a faster work hardening rate and fracture of aluminum matrix. FE-SEM images show that distribution of boron carbide particles in aluminum matrix reaches a full homogeneity when steady state takes place. The better distribution of reinforcement throughout the matrix would increase hardness of the powder. To study the compressibility of milled powder, modified heckel equation was used to consider the pressure effect on yield strength as well as reinforcing role of B4C particles. For better distribution of reinforcement throughout the matrix, r, modified heckel equation was used to consider the pressure effect on yield strength as well as reinforcing role of B4C particles.