Studies On Process And Microstructure Of Continuous C_f/Al Composites Manufactured By Hot Pressing Diffusion Bonding

The continuous Cf/Al composite has been intensively observed by researchersaround the world as one of the structural materials of the highest strategic value innational defense for its high specific strength, specific modulus, expansion coefficientand designability. The wettability between C and Al is poor and the interfacialreaction between C and Al is seriously due to the ultra-high reaction temperature inliquid molding process, which causes the structure and performances Cf/Al compositeare poor. In this paper, continuous Cf/Al composites were prepared by hot-pressingdiffusion bonding, using aluminum foils and powders as matrix respectively, andT300carbon fiber fabric as reinforcement. Effects of parameters on compactness,microstructure and interfacial reaction of Cf/Al composite were studied systematically.The main conclusions are as follows.The continuous Cf/Al composite reinforced by carbon fiber fabrics was preparedsuccessful by hot pressing diffusion bonding. The aluminum and carbon fibers in thetest piece were compactly organized and firmly bound at the interface without theflaws like cracks or pores.The compactness of Cf/Al composite increases as increasing of hot pressingtemperature. Using aluminum foils as the matrix, the parameters for continuous Cf/Alcomposite by hot pressing diffusion bonding are as follows. Hot pressing temperatureis650℃, hot pressing time is20min, pressure is30MPa, and the composite materialcompactness is98.5%. Using aluminum powder as matrix, the parameters optimizedby orthogonal experiments for continuous Cf/Al composite by hot pressing diffusionbonding are as follows. Hot pressing temperature is640℃, hot pressing time is50min,pressure is15MPa, and the composite compactness is98.3%. The composite withaluminum powder as the matrix is relatively more workable in thermoforming with alower forming temperature.Using aluminum foils as matrix, when the hot pressing temperatures is lowerthan650℃, test pieces were poorly formed with no bonding between the aluminumfoils and the carbon fibers, since aluminum can hardly diffuse into the clearanceamong fiber bundles and among individual fibers. Cf/Al composite samples have clearstratification. When hot pressing temperature raises to650℃, hot pressing time is 20min, pressure is30MPa, and aluminum can diffuse into the clearance among fiberbundles and among individual fibers. Carbon fibers distribute in the aluminum matrixevenly.Using aluminum powders as matrix, when the hot pressing temperatures is lowerthan640℃, the diffusion of aluminum happened only on its contacting surface withthe carbon fiber fabric, without touching the clearances between the fiber bundles andbetween the individual fibers. Cf/Al composite samples have clear stratification. Whenhot pressing temperature raises to640℃, hot pressing time is50min, pressure is15MPa, aluminum completely diffuses into fiber bundles and individual fibers withthe fibers evenly distributed in the aluminum matrix, creating a firm bonding at theinterface.The generation of Al4C3yielded by the interfacial reaction increases asincreasing of hot pressing temperature. Using aluminum foils as matrix, theparameters of continuous Cf/Al composite prepared by hot-pressing diffusion bondingare as follows. Hot pressing temperature is560℃, hot pressing time is35min,pressure is30MPa, interfacial reaction product Al4C3accounts for1.3%. Usingaluminum powder as matrix, the parameters of hot pressing technique optimized byorthogonal experiments with aluminum as the matrix are as follows. Hot pressingtemperature is560℃, hot pressing time is20min, hot pressing pressure is20MPa,interfacial reaction product Al4C3accounts for1.4%.By generally observing the influence of compactness and microstructure of theCf/Al composite and interfacial reaction, the optimized parameters for preparingcomposite with aluminum powder as the matrix are as follows. Hot pressingtemperature is640℃, hot pressing time is50min and hot pressing pressure is15MPa.