Effect of extrusion treatment on the microstructure and mechanical behavior of SiC nanowires reinforced Al matrix composites

Abstract

In the present work, microstructure and mechanical performance of extruded SiCnw/Al composites have been investigated. The extrusion treatment leads to the alignment of SiC nanowires and the densification of the composites. The average length of SiC nanowires has been shortened after extrusion. High density dislocation tangles have been observed in Al matrix after extrusion. As the “non-deformable” phases, SiC nanowires inhabited the movement and deformation of surrounding Al matrix, leading to the formation of the grain boundaries. Therefore, SiC nanowires were mainly found at the boundary of Al grains in the extruded composites. Regardless of content of SiC nanowires, the yield strength, tensile strength and elongation of SiCnw/6061Al composites have been improved after extrusion treatment. Based on generalized mixture rule considering the effect of porosity, the increase of elastic modulus of SiCnw/6061Al composites is mainly due to the densification effect. The strengthening factor and efficiency of SiC nanowires are highest among all SiC reinforcements, and the strengthening behavior of SiC reinforced Al matrix composites could be well explain by the modified shear-lag model. The ratio of strengthening efficiency of SiCnw/Al composites before and after extrusion was about 0.6, indicating that orientation optimization of SiC nanowires is an effective method to improve the mechanical properties of SiCnw/Al composites.