Characterization of Al/Gr composites synthesized via flake powder metallurgy

Aluminum/graphite (Al/Gr) composites due to their low density and excellent tribological properties have gained many applications in aerospace and automobile industries. In the present study, for the first time, a relatively new technique termed as flake powder metallurgy was utilized for processing of these composites. In the first stage, two different sized Al powder particles were mechanically milled in a planetary ball mill up to 9h. After each one hour of milling, powder samples were subjected to sieve analysis, laser particle size analysis and SEM to find the optimum milling time. The microhardness of powders were quantified at some milling time increments to investigate the effect of the initial powder size and milling time on the extent of work hardening and grain refinement occurred during milling. In the second stage, green compacts of Al flakes containing different percentages of flake-shaped Gr particles were prepared. In these compacts, the Al and Gr flakes were aligned in such a way that their largest surfaces were in touch with each other. These compacts were cold pressed (in a direction normal to the flakes) and sintered at optimized pressure and temperature. Optical microscopy and SEM revealed a uniform and aligned distribution of Gr particles within the matrix alloy. The different microhardness, hardness and porosity values obtained for these composites were rationalized in terms of their Gr and porosity content as well as the initial size of Al powders and the milling time used for preparation of these composites.

کلیدواژه ها:

Al/Gr composites ، Flake Powder Metallurgy ، Milling ، Hardness ، Porosity