Fabrication of nanostructured Al-Al4C3 alloys.

Aluminium and graphite elemental powder mixtures containing 2.2 and 4.5 wt. % graphite were milled using a planetary ball mill in order to produce nanostructured Al-Al4C3 alloys. The structural evolution of powder particles was studied by x-ray diffractometry and hardness measurements. The results showed that Al4C3 compound could not be synthesized only by milling process. A suitable subsequent heat treatment was required to allow Al-graphite reaction to take place kinetically. The heat treatment time and/or temperature decreased as milling time increased. Milling process also leads to the refinement of aluminium grain size to a nanoscale size of ~25 nm. This structure remainded unchanged upon heating due to the formation of Al4C3 particles, which hinder the grain growth process. The Al4C3 particles formed during heat treatment had a size of ~15 nm causing a remarkable increase in hardness of Al matrix.