Manufacturing of functionally graded metal matrix composite materials by segregation

Abstract

By applying vibrations to a granular media differing in size and density, various segregation states can be established. If an additional rotational motion is engaged, the effective force is no longer gravity but a centrifugal one, leading to a radial segregation. In this contribution, an experimental setup is presented which utilizes these effects. This setup is used to produce a cylindrical metal matrix composite consisting of silicon carbide and aluminium having a radial gradient. The influence of different material- and process-specific parameters on the segregation behaviour was investigated. The evaluation of micrographs of the pressed and sintered samples shows that both positive and negative gradients can be achieved. The rotation speed and the grain size ratio were identified as significant factors. The variation of the vibration amplitude leads to opposite effects. On the one hand, the gradient intensity increased. On the other hand, the variances of the SiC distribution in the tangential or radial directions increased as well. In addition, it has been shown that the effects of different grain shapes are marginal.

Review on developments of bulk functionally graded composite materials

“…As the diamond particle vol.-% increases from 10% to 25%, the area fraction of the diamond particles in the outer periphery of a wheel cast at 1393 K under 78G increases from 1.8% to 5.1%. Behrens and Bohr [230] fabricated Al-SiC FGCMs using a segregation process resulting from the vibration of a granular mixture of constituents having different sizes and densities. A cylindrical matrix was first filled with a mixture of the constituent powders.…”