Effect on microstructures, hardness and SDAS of primary Mg₂Si/Al-Si eutectic phases of centrifugally cast functionally graded Al-(Mg₂Si)p in-situ composites

In the present study, the centrifugal casting route was employed to synthesize the Al-(Mg₂Si)p functionally graded in-situ composites at 1200 rpm rotating speed of mold. The formation of primary Mg₂Si particles/Al-Si eutectic phases by the in-situ chemical reaction has been investigated. In the Al-Mg-Si alloys system, in-situ formed Mg₂Si particles are lately introduced a new aspect, because of due to lighter density (1.99 gm/cm³) than Al-matrix (2.27 gm/cm³) the Mg₂Si particles are more capable of migrating into inner zone of cast tubes due to centrifugal force. The X-Ray diffraction (XRD) technique was carried out to confirm the presence of in-situ formed Mg2Si/Si particles in the cast composites. Optical microscopy analysis was carried out to reveals distribution, size and volume fraction of Mg₂Si particles of cast cylindrical tubes. Scanning electron microscopy (SEM) analysis was also carried out to reveal the morphological characteristics and some intermetallics (π & β phases) present into the cast FGM tubes. The Vickers hardness test was carried out along the radial direction of tubes. Resultant, the hardness value is remarkably improved by 20% to 30% at the inner zone due to high volume percent of reinforced primary Mg₂Si hard particles. The objective of this investigation was to observe the effect on microstructures, hardness and secondary dendrites arm spacing (SDAS) of Mg₂Si particles/Al-Si eutectic phases of fabricated FGMs tube and analyzed their gradient properties. (paper)