Reinforced Phase Dispersion And Interface Behavior Of SiCp/Al-Cu-Mg Composites

The application of aluminum alloy drill pipe in deep well/ultra-deep well and acid oil and gas wells is very extensive,but its application is limited because of its poor wear resistance and low temperature strength.SiC particles with high strength,high hardness and low cost,the addition of SiC particles in the aluminum alloy can effectively solve the problem that the aluminum alloy drill pipe is easy to wear and easy to soften in the ultra-deep well,which can effectively improve the service life and drilling depth limit of the aluminum alloy drill pipe.But SiC particles and aluminum melt is not infiltrated,resulting in the addition of SiC particles into the aluminum alloy melt difficult and easy to reunite.In this paper,the wetting behavior of SiC/Al interface and the dispersion of SiC particles were investigated by studying the microstructure of SiC(modified)/Al-Cu-Mg composites in as-cast,homogenization and extrusion.On this basis,the heat treatment process parameters were further discussed,and the effects of solid solution and aging parameters on the SiC/Al interface behavior and mechanical properties of SiC(modified)/Al-Cu-Mg composites were investigated.The research results of this paper can provide basic data and theoretical guidance for the optimization of the modified process and the solution-aging process parameters for the industrial production of SiC particles reinforced aluminum matrix composites by using"vacuum melting-vacuum casting-homogenization-extrusion-solid-aging" process,It is of great significance to the research and development of lightweight materials for oil drill pipe.In this paper,SiC particles were modified by high temperature oxidation method and surface electroless nickel plating method.The particle size and microstructure of SiC particles before and after modification were analyzed by laser particle size analyzer,SEM and XRD;Using the modified SiC particles as the reinforcing material,6.5 wt.%SiCp/Al-Cu-Mg ingot with diameter of 82 mm was prepared by ZG-25 vacuum intenrmediate frequency electromagnetic induction furnace.The composites were homogenized at 465 ? and 24 h,and then a sheet of 6.5 wt.%SiCp/Al-Cu-Mg with a cross-sectional size of 20 × 10 mm was prepared at a melt ratio of 30:1 at 450 ? using a horizontal aluminum extruder.The effects of the modification process on the wetting behavior of SiC/Al interface and the dispersion of SiC particles were investigated by SEM,XRD and EDS.The melting temperature of the low melting point phase in SiCp/Al-Cu-Mg was determined by DSC as described in the as-cast and homogenized state,on the basis of this,the heat treatment was carried out on 6.5 wt.%SiCp/Al-Cu-Mg with different solution and aging parameters.The mechanical properties of 6.5 wt.%SiCp/Al-Cu-Mg treated by different heat treatment systems were tested by microhardness tester and universal tensile testing machine.The morphology of the tensile fracture and the microstructure of the SiC/Al interface were observed by SEM,and the optimum heat treatment parameters of 6.5 wt.%SiCp/Al-Cu-Mg were obtained.The results show that:(1)SiC particles with high temperature oxidation treatment and surface electroless nickel plating can improve the melt wettability of aluminum alloy with the modified silicon carbide,and SiC particles can be added to the aluminum alloy melt;The ratio of the proportion of the SiC particles after the oxidation treatment to the aluminum melt is 1.09,and the ratio of the proportion of the SiC particles after electroless nickel plating to the aluminum melt is 1.45,therefore,the addition and dispersion of SiC paritcles in Al-Cu-Mg matrix after chemical nickel plating treatment are worse than those of SiC particles after oxidation treatment.(2)The SiC particles modified by nickel plating are mainly distributed in the grain boundary of 6.5 wt.%SiCp/Al-Cu-Mg composites,and the distribution is uniform.In the as-cast 6.5 wt.%SiCp/Al-Cu-Mg composites,the oxidized SiC particles are distributed in the grain boundaries and grains of the aluminum matrix,but the SiC particles at the grain boundaries are more homogeneous than the SiC,and the distribution of SiC particles is uniform;The SiC particles after the extrusion treatment were distributed in the extruded direction in 6.5 wt.%SiCp/Al-Cu-Mg extruded materials.(3)6.5 wt.%SiCp/Al-Cu-Mg extruded material was heat-treated at 510 ? for 2 h and quenched by water then at 120 ?for 24 h and air-cooled.The tensile strength of the SiCp/Al-Cu-Mg extruded material was 627 MPa and the microhardness was 132.7 HV after the treatment.After the heat treatment,the distribution of SiC particles in the aluminum alloy is changed from the original grain boundary to the crystal.(4)During the vacuum melting process,the oxide film on the surface of the SiC particles reacts with the aluminum liquid to form the ingotstone(MgAl2O4),at the same time,no brittle phase formation of Al4C3 was found.The silicon dioxide produced by high temperature oxidation is very good to protect the silicon carbide particles from aluminum liquid erosion,and the SiC/Al interface states were stable during homogenization,hot extrusion and T6 heat treatment,and no other new interface products were formed.