Processing and mechanical properties of lamellar-structured Al–7Si–5Cu/TiC composites

Abstract

Inspired by nacre, we designed biomimetic metal–ceramic composites in which hard and ductile phases were alternately arranged. We first prepared lamellar-structured TiC scaffolds with 25, 30 and 35vol% solid loadings using a unidirectional freeze casting technique and then measured wetting and infiltration dynamics for a commercial Al cast alloy, ZL107, with the main composition of Al–7Si–5Cu on the porous TiC scaffold using a modified sessile drop method at 850°C. The wetting was affected by liquid spreading at horizontal surface and infiltration in depth, while the latter played a dominant role in the decrease in contact angle. On the basis of the wetting results, the lamellar ZL107/TiC composites were successfully fabricated by pressure infiltration of the molten ZL107 alloy into porous TiC scaffolds and their mechanical properties were evaluated. The compressive strength and elastic modulus increased while bending strength decreased with increasing TiC content, giving maximum values of 1166±20MPa, 205±2GPa and 363±5MPa, respectively. Formation of (Alm,Si1−m)3Ti, Al3Ti and Al4C3 phases in the composites was presumed to deteriorate the toughness of the composites, leading to brittle fracture under loading.