Synthesis and structural characterization of Al-B4C nano-composite powders by mechanical alloying

This paper consists of two parts. In the first part, attrition milling of commercially available (0.7 μm) boron carbide (B4C) particles was optimized to prepare B4C nano-particles. In the second part of the study, mechanical alloying was successfully employed to synthesize metal matrix composite powders with a nanocrystalline Al 6061 alloy as the matrix and B4C as the reinforcement. Different amounts of B4C particles (5 wt.% and 10 wt.%) having various sizes of 90 nm (produced in the first part of study), 0.7 μm and 1.2 μm were mixed with different sized (21 μm and 71 μm) Al 6061 powder particles and they were milled for different times. The results showed that the nano-sized B4C particles may be fabricated when they were milled for 110 h. The size of powder particles in the milled powder mixture was affected by the initial size and content of B4C particles and Al powders. The SEM and TEM micrographs demonstrated a uniform distribution of B4C particles in aluminum powders after 8 h milling of an Al + B4C powder mixture. XRD results confirmed that the crystal size of aluminum reached to 57 nm after 16 h milling of powder mixture and addition of B4C resulted in a finer grain size of Al in the Al + B4C mixture during the early stages of milling.