FABRICATION AND MECHANICAL-PROPERTIES OF ALUMINUM MATRIX COMPOSITE-MATERIALS

Aluminum matrix composite materials containing SiC whisker and Saffil alumina short fiber are fabricated by the direct squeeze infiltration method. Optimum processing conditions for preforms and squeeze casting are suggested. For minimum damage of the reinforcements, the relatively low pressure of 25 MPa is applied. Mechanical properties, such as Young's modulus and ultimate tensile strength, are improved up to 80% by the addition of reinforcements. As expected, strength of MMCs decreases with increased testing temperatures. However, these composites have reasonable strength values for high temperature applications. Predictions for elastic modulus and tensile strength of composites fabricated by the direct squeeze infiltration method are proposed from the transformed laminate analogy, and combinations of modified rule of mixtures and shear lag theory, respectively. Proposed predictions show good agreement with experimental data. From fracture surface analyses at room and elevated temperatures, it is found that failure mode is ductile on the microstructural level and it becomes more ductile as temperature of testings increases. Based on fracture surface observations and experimental data, strength reductions at elevated temperatures appear to be mainly due to overaging and softening of the matrix alloy.