The Exploration Of Fabrication Process And Investigation Of Properties Of Short Carbon Fiber Reinforced Aluminum Matrix Composites With Low Content Carbon Fiber

Carbon fiber reinforced aluminum composite has been identified as an ideal structural material due to its high specific strength,specific modulus,good ductility,low expansion coefficient,which has been widely used in the aerospace and automotive industries.In this study,the short carbon fiber reinforced 2024 aluminum composites(C_f/2024)were fabricated by vacuum hot press sintering(VHP)and electromagnetic stirring remelting after liquid stirring casting method respectively.The microstructures of C_f/2024 aluminum composites were observed and analyzed with optical microscope(OM),scanning electron microscope(SEM),EDS energy spectrum and XRD analysis technology.The actual density of C_f/2024 aluminum composites was measured with Archimedes principle,and the hardness,mechanical properties and micro-yield strength were measured with Vickers hardness tester,quasistatic tensile test and loading-unloading tensile test.The results showed that:The optimal VHP process parameters were sinter temperature of 450?,sinter time of 50 Minutes and 50 MPa of sinter pressure.The composites sintered with optimal process parameters had highe compactness,fine grain size and a density that similar to the theoretical density.The carbon fibers were mainly arranged along the vertical direction of the hot pressing pressure at a small angle and had excellent interface bonding with a-Al matrix.The peak aging treatment process(T6 process)of the fabricated C_f/2024 aluminum composites and 2024 matrix alloy with VHP method was 495 ? × 2 h + 180 ? × 10 h.The 3.0 wt.% C_f/2024 aluminum composites referneced with Cu-coated carbon fiber had a hardness of 167.8 HV after treated with peak aging process,which was increased by 10.5% compared with 2024 alloys fabricated with same VHP process.However,the brittle intermetallic compound of Al2 Cu or AlCu were formed at the interface between the carbon fiber and a-Al matrix due to the inter difficusion of Cu and Al in a-Al matrix during hot press and heat treatment.The brittle intermetallic compound of Al2 Cu or AlCu was easily breaked and decreased the bonding between the carbon fiber and matrix,which results in a decrease in the mechanical properties of the 3.0wt.%C_f/2024 aluminum composites,even though they had higher hardness.The thermal coefficient of expansion of C_f/2024 aluminum composites fabricated with VHP method was obviously decreased compared with 2024 alloys.The C_f/2024 aluminum composites referenced with Cu-coated short carbon fiber had lower thermal coefficient of expansion than that referenced with Cu-uncoated short carbon fiber.The reason is that the stronger interface bonding between the Cu-uncoated carbon fiber and a-Al matrix had higher restriction effect on the expansion of a-Al matrix.Electromagnetic stirring remelting after liquid stirring casting didn't changed the distribution of carbon fiber in a-Al matrix and the interface bonding between the Cuuncoated carbon fiber and a-Al matrix.And the electromagnetic stirring remelting decreased the content of impurity element and brittle intermetallic compound on grain boundaries.The grain of a-Al matrix was refined due to the high cooling rate of copper crucible.Therefore,the mechanical prpperties of 3.0 wt.% C_f/2024 Sc aluminum matrix composites were increased after electromagnetic stirring remelting.It shows that it is favor to improve the microstructure and mechanical properties for 3.0 wt.% C_f/2024 Sc aluminum matrix composites fabricated with liquid stirring casting method after electromagnetic stirring remelting.The strength and ductility of 3.0 wt.% C_f/2024 Sc aluminum matrix composites fabricated with liquid stirring casting method were higher than that fabricated with VHP method.The tensile strength,yield strength and modulus of elasticity of materailas after electromagnetic stirring remelting is 505.0 MPa ?415.3 MPa and 82.3GPa.All of them were higher than that fabricated with liquid stirring casting method.Whether or not the 3.0 wt.% C_f/2024 Sc aluminum composites were remelted with electromagnetic stirring,the materials had similar micro-yield behavior.The micro-yield strength of 3.0wt.% C_f/2024 Sc aluminum composites had similar trend as that of macro yield strength and tensile strength with aging time.After treated with peak aging process(T6 process),the 3.0 wt.% C_f/2024 Sc aluminum composites had a micro-yield strength of 310 MPa,which increased by 11.8% compared with that with conventional liquid stirring casting method.