Microstructure and mechanical properties of reaction squeeze cast hybrid Al matrix composites

Hybrid Al matrix composites reinforced with Kaowool ceramic fiber (Al2O3. S iO2) and reaction formed intermetallic compound particles, starting composi tions of (10%Al2O3. SiO2+5%Ni)/Al and (10%Al2O3. SiO2+5%TiO2)/Al were fabri cated employing squeeze casting technique. Microstructures of the Al compos ites were examined, and the reactivity of Ni and TiO2 powders added to Kaow ool short fiber preform with infiltrating molten Al, resulting products of Al3Ni and Al3Ti, during squeeze casting was analyzed. Hardness, strength (a t 25 and 300 degreesC) and wear resistance of the composites were character ized. To investigate the fracture behavior of the composites, in-situ fract ure test was performed within SEM. The hybrid Al composites revealed the mi crostructure of uniformly distributed reinforcements (ceramic short fiber a nd reaction formed intermetallic compounds). Ni powder added hybrid Al comp osite achieved the highest hardness, strength and wear resistance among the composites. It was found that the strength drop at elevated temperature (3 00 degreesC) is effectively reduced by hybridization with ceramic fiber and intermetallic compounds reinforced in Al. In-situ fracture observation dem onstrated the fracture behavior of Ni powder added hybrid Al composite as m icrocrack initiated mainly by short fiber/matrix interfacial debonding and the crack propagated through the cluster of intermetallic compound particle s as loading is raised.