Study On Process,Microstructure And Mechanical Properties Of 304 Stainless Steel/Pure Aluminum Bimetal Composite Casting

Bimetallic composite materials are prepared by metallurgical bonding of two different materials at the interface.Bimetallic composites can simultaneously possess the excellent properties of both materials,and they have broad applications in modern rapidly developing industrial production.Aluminum and steel are two commonly used metals in industrial production.Aluminum has advantages such as low density,good corrosion resistance,and high thermal conductivity,but it has low strength and poor wear resistance.On the other hand,steel has high strength and good ductility,but it has a higher density.By combining these two materials into a composite,it is possible to reduce weight,improve strength,and retain the advantages of aluminum,making it suitable for various industrial applications.This study utilizes a liquid-solid composite casting method to prepare 304stainless steel/pure aluminum bimetallic composite materials.Firstly,the stainless steel tube matrix is subjected to hot-dip aluminum plating.Then,the plated steel tube is used as the matrix material,and pure aluminum melt is poured into it,followed by heat treatment,to explore the optimal process for preparing stainless steel/pure aluminum bimetallic composite materials using this method.The interface structure of the composite materials is observed and analyzed using scanning electron microscopy（SEM）,energy-dispersive spectroscopy（EDS）,and X-ray diffraction（XRD）.The mechanical properties of the composite materials are tested using a microhardness tester and an electronic universal material testing machine.The influence of the hot-dip plating process,casting process,and annealing process on the interface structure and properties of the composite materials is studied,and the intrinsic relationship between microstructure and mechanical properties is summarized,providing a theoretical basis for the preparation of high-performance stainless steel/pure aluminum composite materials.When the temperature of hot-dip aluminum plating is low and the duration is short,a continuous bonding layer may not form on the surface of the steel tube substrate,and a large number of defects may exist.As the hot-dip plating temperature increases and the hot-dip plating duration is prolonged,a complete and continuous bonding layer can be formed on the steel tube surface,and the thickness of the bonding layer increases.However,when the hot-dip plating temperature is too high or the hot-dip plating duration is too long,cracking may occur in the bonding layer,and the thickness of the steel tube wall may decrease,resulting in a decrease in the smoothness of the coating.When the hot-dip plating temperature is 760°C and the hot-dip plating duration is 10 minutes,a dense and uniform bonding layer can be obtained,mainly composed of Fe Al₃ and Fe₂Al₅ phases.At this condition,the quality of the aluminum coating on the steel tube surface is also the best.Preparation of composite materials from hot-dipped aluminum-plated steel tubes as inlays for liquid-solid composite casting.When the casting temperature increases or the liquid-solid volume ratio increases,the thickness of the bonding layer also increases.However,when the casting temperature is low and the liquid-solid volume ratio is small,gaps may appear in the bonding la yer,resulting in poor performance of the composite material.When the liquid-solid volume ratio is too large,the thickness of the bonding layer increases sharply,and the bonding quality of the interface deteriorates,resulting in a significant decrease in mechanical properties.With the increase of casting temperature and liquid-solid volume ratio,the hardness change of the base materials on both sides of the composite material interface is small and basically stable,while the hardness of the bonding l ayer at the interface continues to increase.The tensile strength and shear strength of the composite material show a trend of first increasing and then decreasing with the increase of casting temperature and liquid-solid volume ratio.When the casting temperature is 740°C and the liquid-solid volume ratio is 6.9,the microstructure and properties of the composite material reach the optimum.At this time,the thickness of the bonding layer is 19.4μm,and Fe Al,Fe Al₂,Fe Al_3,Fe₂Al₅,and Fe₃Al phases are formed in the bonding layer.The microhardness at the interface of the composite material under this process is572.9 HV,and the tensile strength and shear strength are 512.3 MPa and 41.6 MPa,respectively.After annealing treatment of the composite materia l,it was found that the thickness of the bonding layer at the interface increased with the increase of annealing temperature and annealing time.The influence of annealing temperature on the bonding layer thickness was more significant.The harmful alumin um-rich phases in the bonding layer included Fe Al₂,Fe Al₃,and Fe₂Al₅.The tensile strength and shear strength of the composite plate decreased with the increase of annealing temperature and annealing time.At 440℃annealing for 1.5 hours,the thickness of the bonding layer slightly increased to 20.8μm compared to the non-annealed state.At this condition,the tensile strength decreased compared to the annealed state,while the shear strength increased slightly.The comprehensive mechanical properties were optimized,with a tensile strength of 483.6 MPa and a shear strength of 49.2 MPa.