Preparation Of Layered Carbon Fiber Reinforced Aluminum Matrix Composites By Ultrasonic Vibration

In recent years,carbon fiber reinforced aluminum matrix(Cf/Al)composites have been widely applied in the field of structural materials because of its high modulus and specific strength,structure designability and thermal conductivity.So far,many scholars have carried out a series of researches on the manufacturing method of Cf/Al composites.Hot pressing method,squeeze casting method and gas pressure infiltration method were studied adequately.Through the analysis of the existing preparation process of Cf/Al composites,it can be known that these preparation processes have the disadvantages of long period,complex operation,long reaction time between carbon fiber and matrix metal,and great damage to carbon fiber.Therefore,a new method of manufacturing Cf/Al composites by ultrasonic vibration is proposed in this thesis.Therefore,Cf/Al composites were fabricated by ultrasonic vibration method.The microstructure and properties of Cf/Al composites were analyzed by scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and multifunctional electronic drawing machine.The formation mechanism of microstructure and the influencing factors of mechanical properties were studied.The results show that ultrasonic vibration can produce high pressure and high speed liquid flow in the local liquid metal.Cf/Al composites with uniform microstructure and good bonding between carbon fiber and matrix can be successfully prepared by using self-made preform.It is found that the pre-applied stress of carbon fiber had a certain influence on the preparation of Cf/Al composites and the effect of pre-applied stress of Cf/Al composites were studied.The size of un-infiltrate defects in the Cf/Al composites decreased first and then increased with the increasing of pre-applied stress.When the pretension stress is 4N,the carbon fiber can achieve uniform distribution,and its tensile strength can reach 243.6MPa.The analysis shows that the pre-applied stress is too small that the carbon fiber deviates from the flow center of the liquid metal produced by ultrasonic wave,and the ultrasonic wave can not act uniformly on the carbon fiber,the infiltration of carbon fiber by aluminum can not be realized.When the stress is too large,the fiber will gather in the matrix,and the fiber will resist ultrasonic wave,which makes the liquid aluminum can not immerse in the partial interspace of the collective fibers.When the pre-applied stress is 4N,the carbon fiber can be dispersed uniformly in molten aluminum during the preparation process,which makes the liquid aluminum infiltrate the interspace.The experimental results show that fiber arrangement has great influence on the properties and fracture modes of layered carbon fiber reinforced aluminum matrix composites.When tensile along the direction parallel to the bottom carbon fiber,As the angle between the top carbon fiber and bottom carbon fiber varies by 0°,30°,45°,60° and 90°,the tensile strength of composites decreased to a maximum of 238.6MPa,and the fracture mode of carbon fiber composites changed from fiber pull-out to that of fiber pull-out combined with interface-fiber composite fracture or exfoliation along the interface.The tensile strength of the composites increases with the change of the angle between 0° and 90° in the direction perpendicular to the bottom layer.The maximum tensile strength of the composites is 160.3MPa.The fracture mode of carbon fiber composites changed from exfoliation along the interface to that of exfoliation along the interface combined with interface-fiber composite fracture or fiber pull-out.