Studies on the fracture and flexural strength of Al/Si p composite

Abstract

Pure aluminum matrix composite reinforced with a high volume fraction of silicon particles (Al/Si p) was fabricated by gas-pressured infiltration. The results of four point flexural strength tests show that Al/Si p has low flexural strength. The analysis of the fractograph reveals the fracture mechanism of Al/Si p. The fracture of Al/Si p is primarily dominated by the fracture of brittle silicon particles and the subsequent link up of damage through the matrix. The pre-existent microcracks in silicon particles that were made during the process of compacting will also lower the flexural strength of Al/Si p composite. The hybrid particle reinforced pure aluminum matrix composite (Al/Si p+SiC p) was fabricated in the same way. Results show the flexural strength can be improved by 11.3% compared with Al/Si p when 6 vol.% silicon particles are replaced by silicon carbide particles with the same volume fraction and size. The reason is that SiC p with higher fracture stress and higher elastic modulus can prevent the rapid expansion of cracks through the composite and lower the stress in silicon particles.