THE EFFECTS OF PROCESSING PARAMETERS ON MECHANICAL-PROPERTIES OF SICW2124AL COMPOSITES/

The aluminium alloy matrix composites with discontinuous ceramic reinf orcements are regarded as potential materials for high-performance str uctural parts in aerospace and automobile industries. The processing p arameters related with complicated fabrication process of metal matrix composite need to be strictly controlled to produce composites with r eproducible and uniform mechanical properties for industrial applicati on. The understanding of the relationships among processing parameters - microstructures - mechanical properties is very important to produc e reliable metal matrix composites. In this paper the effects of proce ssing parameters, i.e., volume fraction of whiskers, vacuum hot pressi ng temperature, Vacuum hot pressing pressure, extrusion temperature an d extrusion ratio, on mechanical properties of SiCW/2124Al composites fabricated by powder metallurgy process were investigated using a stat istical technique known as Taguchi method. The vacuum hot pressing tem perature was found to be the most sensitive parameter to the tensile s trength. As the Vacuum hot pressing temperature increased up to 570 de grees C, the tensile strength increased due to the enhanced densificat ion of composite and increased aspect ratio of SiC whiskers, which wer e resulted from the reduced strength and increased amount of liquid ph ase in matrix with increasing vacuum hot pressing temperature. The opt imum vacuum hot pressing pressure was considered to be 70MPa, below wh ich the remaining voids reduced the tensile strength of SiCW/2124Al co mposite. The tensile strength increased with increasing volume fractio n of SIC whiskers. However, the volume fraction of whiskers more than 20% was not helpful to increase the tensile strength since the whisker s tend to be non-uniformly distributed. The extrusion temperature need to be higher than the solidus temperature of 2124Al matrix to reduce the damage of whiskers and to improve the alignment of whiskers. The e xtrusion ratio of 15:1 resulted in the highest tensile strength. The a lignment of whiskers improved with increasing extrusion ratio, while t he aspect ratio of whiskers decreased due to the damage of whiskers.