STUDIES ON SYNTHESIS AND CHARACTERIZATION OF IN-SITU Al-12%Si-TiB2 METAL MATRIX COMPOSITES

Abstract

In-situ methods have been developed to synthesize ceramic reinforced metal matrix composites (MMCs), so as to eliminate the inherent problems associated with conventional ex-situ processes. The main objective of present research was to synthesize, characterize and study the manufacturability of in-house produced in-situ Al-12%Si/TiB2 MMCs for possible industrial applications. The Al-12%Si/TiB2 MMCs were fabricated through synthesized through hybrid flux-assisted synthesis technique. Microstructural characterization revealed that the of titanium diboride (TiB2) reinforcements were uniformly distributed inside the Al-Si matrix and were dominantly in the form of hexagonal like structure. X-ray diffraction (XRD) studies confirmed the existence of TiB2, without any presence intermetallic phases in the composite specimen. The developed MMCs were subjected to the mechanical testing as per the ASTM standards. Incorporation of TiB2 reinforcement enhanced the mechanical strength of Al-12%Si matrix significantly with a reduction in the ductility and the properties increase with increasing TiB2 volume fraction. The fracture surface of the tensile specimen was analyzed using scanning electron microscopy (SEM) confirms the failure in Al-12%Si/TiB2 composites mainly due to clustering, decohesion of matrix phase and TiB2 particles. These weak sites favour microcracks to grow rapidly, hence decrease the ductile nature of composites. Transmission electron microscopy (TEM) analysis indicated that in-situ formed TiB2 particles were faceted shaped with a dominant number of nanosized ceramic particulates.