Effects of hot extrusion parameters on the tensile properties and microstructures of SiCw-2124Al composites

The effects of extrusion ratio and extrusion temperature on tensile strengths and microstructures of 20 vol.% SiCw-2124Al composites were investigated. The alignment of SiC whiskers along the extrusion direction in SiCw-2124Al composites was improved and the aspect ratio of SiC whiskers was decreased with increasing extrusion ratio from 10:1 to 25:1. The SiCw-2124Al composite exhibited the highest tensile strength at the extrusion ratio of 15:1. The aspect ratio of whiskers and the relative density of composite increased with increasing extrusion temperature from 470 °C to 530 °C. The tensile strength of SiCw-2124Al composite increased with increasing extrusion temperature up to 530 °C. Based on the concept of the load transfer efficiency of misoriented SiC whiskers in the 2124Al matrix, the two microstructural parameters of the alignment and aspect ratio of whiskers, which influenced on the tensile strength in an opposite way, were combined into a single parameter proposed as an effective aspect ratio. The highest tensile strength of SiCw-2124Al composite at the extrusion ratio of 15:1 is explained by the largest effective aspect ratio due to the balance of the alignment and aspect ratio of SiC whiskers. A modified phenomenogical equation describing the tensile strength of SiCw-2124Al composites as a function of microstructural parameters was proposed by introducing the effective aspect ratio as a substitute for the average aspect ratio of SiC whiskers.