Fabrication of carbon fiber oriented al-based composites by hot extrusion and evaluation of their thermal conductivity

Abstract

New heatsink materials having higher thermal conductivities have recently been required due to the recent rapid improvements in performance of the central processing unit, CPU, with increasing heat generation from computer devices. As an alternative material to conventional heatsink materials such as Al and Cu, composites containing carbon fibers have recently been gaining much attentions because of their extremely high thermal conductivity. However, the carbon fiber exhibits high thermal conductivity only in its longitudinal direction. Therefore, it is essential to control the orientation of the carbon fibers in the composite materials. In the present study, hot extrusion of a powder?fiber mixture is applied to realization of unidirectional array of carbon fibers in Al matrix, and the effects of volume fraction of carbon fiber on the thermal conductivity of the carbon fiber oriented Al?based composite have been investigated. It has been demonstrated that the carbon fibers are unidirectionally oriented in the extrusion direction, and consequently, the thermal conductivity in this direction increases with the increase in volume fraction of the carbon fiber. For the composites with more than 30 vol? carbon fiber, the addition of Al?Si alloy powder or the application of the spark plasma sintering, SPS, before extrusion was found to be effective for improving the sinterability of the powder-fiber mixture.