The Study On Microstructure And Mechanical Properties Of C_f/Al Composites Prepared By Different Matrix Alloy

Owning to their combined advantages of lightweigh,high specific strength,high specific stiffness,excellent temperat performance and corrosion resistance,continuous carbon fiber reinforced aluminum matrix composites(Cf/Al composites) are important material with great potential in aerospace and national defense industry.Currently,vacuum pressure infiltration method is the mainly near net forming technology of Cf/Al composites,but carbon fiber and aluminum alloy matrix have poor wettability,the extent interfacial reaction can not be control easily in pressure infiltration.Therefore,to achieve complete infiltration of liquid aluminum and reduce the interfacial reaction of C and Al is the priority issue for the preparation of vacuum pressure infiltration method of Cf / Al composites. At present,there are ways to solve the problems,infiltration temperature control preheating temperature,carbon fiber surface coating and join in the matrix alloy alloying elements, etc.This paper studies the effects of matrix alloy on microstructure and mechanical properties of Cf / Al composites.In this paper,reinforcing material was graphite fiber M40 and matrix alloys were ZL102,ZL114 A,ZL205A,ZL301 aluminum alloys,prepared by the vacuum pressure infiltration of Vol. 40% Cf/Al composites.To study the effects of matrix alloy on microstructure and mechanical properties of Cf/Al composites,the relative density,microstructure,phase composition and elemental distribution and mechanical properties were examined by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),x-ray diffract meter(XRD), analytical balance(EDS),etc.The densification mechanism and fracture mechanism of vacuum pressure infiltration process was theoretical analyzed.The following researches:The fibers have a equal division in Cf/ZL301 composites,and no obvious hole defects were found in microstructure of Cf/ZL301 composites.A small amount of fibers in Cf/ZL102 composites and Cf/ZL114 A composites got together,and tiny infiltration holes hung around the interstices of fibers.A large amount of fibers in Cf/ZL205 A composites got together,and obvious hole defects were found in microstructure of Cf/ZL301 composites.In the four Cf / Al composites prepared under the same infiltration condition by ZL102,ZL114 A,ZL205A and ZL301 aluminum alloys,the Cf/ZL301 composites have a maximum relative density for 99.9%,and Cf/ZL102 composites alsoreached a minimum relative density for 96.4%.The composit basically achieved a complete infiltration.The different of densification degree between Cf /Al composites prepared by the different matrix alloy was caused by the different alloy elements of aluminum alloy.A equal division of element Mg in matrix alloy could improve the wettability of carbon fiber and liquid aluminum and reduced the surface energy of liquid aluminum,then liquid aluminum can have a better infiltration of the fibers interstices.A large number of element Si got together in the surface of carbon fibers,reduced the viscosity of liquid aluminum,then increased the mobility of liquid aluminum.Because of the segregation of element Cu in ZL205 alloys,carbon fibers got together,and the liquid aluminum could not have a better infiltration of the area that fibers got together.The fracture surface of Cf/ZL301 composites was uneven and a large number of fibers pulled out,which exhibits a characteristic of ductile fracture.But the fracture surface of Cf/ZL102 composites and Cf/ZL114 A composites was smooth and no fibers pulled out,which exhibits a characteristic of a brittle fracture.The fracture surface of Cf/ZL205 A composites was relatively smooth,a small amount of fibers pulled out,and some fracture surface was stepped pyramids.In four composites,the tensile strength of Cf/ZL301 composites was maximum,reached 670.2 MPa,and was 544.2 Mpa higher than the tensile strength of ZL301 alloys under the same casting.The tensile strength of continuous Cf/ZL205 A composites was 336.9 MPa and was 167 MPa higher than the tensile strength of ZL301 alloys under the same casting.The tensile strength of Cf/ZL102 composites and Cf/ZL114 A composites was low and almost related to the the tensile strength of ZL301 alloys under the same casting.The different of fracture mechanism between Cf/Al composites prepared by the different matrix alloy was caused by the nature of aluminum alloys and the extent of interfacial reaction.Because of the existence of element Mg in aluminum alloys,carbon fiber and aluminum alloy matrix have good wettability,and the reaction of Al and Mg can generation of Al4C3.The interface in Cf/ZL301 composites were moderate. After matrix cracking and interface debonding,Cf/ZL301 composites took a ductile fracture.Because of the segregation of element Cu in ZL205 alloys,a large amount of fibers got together,and some areas, interface were strong,and Cf/ZL205 A composites took a brittle fracture under lower stress.In Cf/ZL102 composites and Cf/ZL114 A composites,a large number of hard and brittle Si got together near the surface and these areas would be crack source,which indicates a brittle fracture under low stress.Based on the experiment of the unidirectiona arrangement of fiber preform,this paper carried out vacuum pressure infiltration of 3D Cf/Al composites with three-dimensional five-directional braided preform by fiber M40 and ZL301 alloys as matrix alloy.The relative density of 3D Cf/Al composites also reached 97.9%,the infiltration between the beams of fibers were better,and the composit basically achieved a complete infiltration.The tensile strength of 3D Cf/ZL301 composites was 665.8MPa,from the macroscopic fracture,s observe,the fracture surface of continuous Cf/ZL301 composites was uneven and a large number of fibers pulled out.The poisson,s ratio of 3D Cf/ZL301 composites was 0.74 and composites had anisotropic.The elastic modulus of 3D Cf/ZL301 composites was 200.5 GPa and was quite with the elastic modulus of steel.