Fabrication of functionally graded Al6061/SiCP composite materials via gravity sedimentation method

Functionally graded materials (FGMs) are characterized by the variation in composition and/or structure over volume, resulting in corresponding changes in their properties along specific directions. In the present investigation the settling velocities of different sized SiC and Al 6061 powder particles in Poly Methyl Methacrylate (PMMA) dissolved in toluene were measured experimentally and the results exhibited a reasonably good agreement with those predicted via the unmodified Stokes law. Then the same gravity sedimentation process was utilized for preparation of Al/SiC compacts by using different sized Al and SiC particles. After burning out the binder, the samples were subjected to cold pressing, sintering, metallographic studies and hardness measurements. The results confirmed that when the ratio of settling velocities of the constituent powders were in a specified range (i.e. V(SiC)/V(Al) ≈ 2.6-3.0), a smooth concentration gradient of SiC particles along the height of samples was created revealing the successful production of FGMs.

Keywords:

Functionally graded composite materials , Gravity sedimentation method , Metal matrix composite , Settling velocity