Fabrication of Functionally graded Al-Si Composites reinforced with Boride Particles

摘要

New polymer/Al-based hybrid composites have been proposed for device production, which require precise fabrication of sputtered Al-Si composite layers reinforced with AlB_2 and AlB_(12) particles because of their tunable elastic modulus. Nonetheless, precise bulk characterization of this sputtered material is lacking when silicon is added. To this purpose, specimens were manufactured via centrifugal casting and conventional vacuum casting (as control samples) using binary Al-Si and commercial Al-B master alloys. The microstructure and mechanical properties were investigated in Al-3wt.Si alloys containing 2 and 3 wt. boron (forming AlB_2 and AlB_(12) particles). Furthermore, differential thermal analysis (DTA) was used to determine the eutectic and melting point temperatures. Eutectic silicon was observed in the matrix as in un-reinforced Al-Si alloys; DTA confirmed the presence of eutectic silicon. DTA also revealed that eutectic silicon has a greater influence than boron reinforcements on the reduction of the melting point of the composites. Composites with AlB_2 particles displayed a functionally graded distribution of AlB_2 particles along the centrifugal direction due to the particle higher density while in the composites containing AlB_(12) the centrifugally-induced segregation was not as effective. Accordingly higher superficial hardness and smaller grain size were observed towards the external regions of the Al-Si-B composites with AlB_2 particles.