Abstract
In order to develop a new aluminum alloy composite which has a low thermal expansion rate and is machinable, the aluminum alloy composites reinforced with short potassium titanate fibers were fabricated. The fiber preform was fabricated and then infiltrated with the AC4A aluminum alloy melt by squeeze casting to fabricate the composite. The microstructure and thermal properties of the composites were investigated. Optical microscopy revealed that the fibers were homogeneously distributed in the alloy. However, the fibers were somewhat in a planar random arrangement parallel to the pressed plane when the fiber volume fraction was high. This is due to the forming of the preform by pressing the upper and bottom of it. The composites were easily machined by the commercial super alloy cutting tools: the composites have good machinability. The thermal conductivity of the composite decreased as the fiber volume fraction increased. At higher volume fraction, the thermal conductivity of the composite in the parallel direction to the pressed plane was higher than that in the transverse direction because of the planar random arrangement of the fibers. The thermal conductivity can be roughly estimated by Landauer‘s model. Average thermal expansion coefficient of the composite decreased as the fiber volume fraction increased. The difference of the thermal expansion coefficient between the parallel and transverse direction to the pressed plane is slight, and the experimental values are in good agreement with the theoretical values calculated by the rule of mixture. These results show that the reduction in the thermal expansion of the aluminum alloy can be accomplished by the reinforcement with the short potassium titanate fibers.
