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

Abstract

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.