Characteristic compressive properties of AlSi7Mg matrix syntactic foams reinforced by Al2O3 or SiC particles in the matrix

Abstract

Metal matrix syntactic foams (MMSFs) were produced by liquid-state low-pressure infiltration. AlSi7Mg alloy was applied as matrix material, while the filler was a set of ceramic hollow spheres (CHSs) or light expanded clay agglomerate particles (LECAPs). The matrix was reinforced by Al2O3 (0.6 mm or 1.2 mm nominal size) or SiC (0.4 mm nominal size) particles. The produced samples were investigated structurally (microstructure) and mechanically (standardized compressive tests). According to the microscopic investigation, liquid-state low-pressure infiltration was found to be a suitable method to produce MMSFs with a reinforced matrix. The shape of the engineering stress – strain curves was mainly influenced by the filler. CHS filled MMSFs showed a high stress peak, while LECAP filling ensured a smoother transition from the linear elastic part to the plateau region. The compressive strength and the structural stiffness of the MMSFs were significantly increased by the reinforcing particles in the matrix. Linear connections were found in the compressive strength – nominal size of the Al2O3 particles and in the structural stiffness – nominal size of the Al2O3 particles relationships. The plateau strength of the MMSFs and thus the absorbed mechanical energy was decreased by the presence of the reinforcement. The decrement was caused by the stress-concentrating particles and could only be equalized by the stronger SiC particles. The failure modes of the MMSFs were dependent on the filler material. Stronger CHS fillers resulted in fracture by cleavage, while the weaker LECAP fillers caused plastic collapse in the samples.