Study On The Process And Its Interface Structure Of Continuous C_f/Al Composites Manufactured By Vacuum Low Pressure Infiltration

Continuous carbon fiber-reinforced aluminum matrix composites are an important material with great potential in aerospace and advanced weapons equipment, and have developed into one of the most strategic structural materials in modern national defense technology because of their combined advantages of lightweight, high modulus, specific strength and good high temperature strength. Currently, squeeze forming and liquid infiltration are two mainly methods for the fabrication of Cf/Al composites, but unfortunately both have common problems such as extremely large forming pressure, difficulty for near net forming of complex components, and so on. Therefore, the near net forming technology is the key technical problem to be solved to ensure the large-scale application of continuous carbon fiber reinforced aluminum matrix composites as complex components.Adopting vacuum low pressure infiltration technique, the present work obtained continuous carbon fiber-reinforced aluminum matrix composites with excellent infiltration effect successfully. The paper investigated the main process parameters of vacuum low pressure infiltration on the influence of sample density. After revealing the key technical factors and their internal mechanism for the formation of immerse defects, the relationship between infiltration integrity and density of composites, as well as their mutual matches, was investigated. On this basis, XRD, TEM, SEM and EDS analysis methods were used to elucidate the phase structures, microstructure and the distribution of different elements in composites. Special emphasis was devoted to the influences of process parameters on the surface of Ni-coated carbon fiber and interface diffusion reactions under low pressure infiltration condition.The results show that vacuum low-pressure infiltration is a simple and stable method for the fabrication of Cf/Al composites and the process parameters are easy to control and adjustable. The basic conditions which affect the forming of Cf/Al composite in vacuum low-pressure infiltration condition were fiber coating and protective atmosphere, vacuum, fiber preheating temperature, and infiltration pressure. Moreover, the key factors are vacuum, fiber preheating temperature and infiltration pressure. Under the conditions of vacuum lOKPa, fiber preheating temperature600℃, the melt infiltration temperature720℃, infiltration pressure400KPa, dwell time10min, the density of Cf/Al composite can reach97.5%. When fulfilled requirements of infiltration, appropriate reduction of the fiber preheating temperature, the infiltration temperature and filling rate of aluminum liquid, or the increase of infiltration pressure, can further eliminate the existence of holes, micro-shrinkages and other microstructure defects in composites, and can even obtain composites with little or nearly no defects. The analysis result of composite interface structure shows that the interface of composites is good combined and smooth, excepting for a small amount of lath brittle phase Al4C3. The damage of Ni coating becomes serious with the increase of fiber preheating temperature. Meanwhile, the diffusion amount of Ni element from coating layer to matrix is enhanced as the increase of infiltration temperature. The formation of Al4C3phase is mainly affected by infiltration temperature, and its content increases as the infiltration temperature increases. Moreover, the content of Al3Ni is enhanced for higher fiber preheating temperature. In addition, infiltration dwell time is another major factor for the formation of Al3Ni and Al4C3phase, and their ratios increase abruptly as the increase of holding time.The investigation results of present paper offer foundation theory for near net forming technology, which can be applied to the preparation of continuous carbon fiber reinforced aluminum composites complex components by vacuum low pressure infiltration.