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 st rengths and microstructures of 20 vol.% SiCw-2124A1 composites were in vestigated. The alignment of SiC whiskers along the extrusion directio n in SiCw-2124A1 composites was improved and the aspect ratio of SiC w hiskers was decreased with increasing extrusion ratio from 10:1 to 25: 1. The SiCw-2124A1 composite exhibited the highest tensile strength at the extrusion ratio of 15:1. The aspect ratio of whiskers and the rel ative density of composite increased with increasing extrusion tempera ture from 470 degrees C to 530 degrees C. The tensile strength of SiCw -2124A1 composite increased with increasing extrusion temperature up t o 530 degrees C. Based on the concept of the load transfer efficiency of misoriented SiC whiskers in the 2124A1 matrix, the two microstructu ral parameters of the alignment and aspect ratio of whiskers, which in fluenced on the tensile strength in an opposite way, were combined int o a single parameter proposed as an effective aspect ratio. The highes t tensile strength of SiCw-2124A1 composite at the extrusion ratio of 15:1 is explained by the largest effective aspect ratio due to the bal ance of the alignment and aspect ratio of SIC whiskers. A modified phe nomenological equation describing the tensile strength of SiCw-2124A1 composites as a function of microstructural parameters was proposed by introducing the effective aspect ratio as a substitute for the averag e aspect ratio of SIC whiskers.