Different SiC_p/HEA Composite Interface Layers On Their Microstructure And Influence Of Mechanical Properties

In order to further improve the strength of AlCrFeCoNi high-entropy alloy(HEA)and the toughness of the alloy,this paper introduces the reinforcement phase of SiC particles(SiCp)into the HEA matrix.Problems such as poor wettability and adverse interface reactions often exist between the reinforced phase SiCp and the alloy matrix.Therefore,this article performs pretreatments such as oxidation and electroless plating on the SiCp surface in order to improve the interface bonding of the composite material,thereby further improving the mechanical properties of the composite material,and providing reference and guidance for the development and industrial application of particle-reinforced metal matrix composites.Spark plasma sintering technology(SPS)was used to prepare SiCp/HEA composites.The phase structure and microstructure of the composite were characterized by X-ray diffraction(XRD),Scanning electron microscope(SEM)and energy dispersive spectroscopy(EDS).At the same time,the interfacial bonding strength,compressive strength,hardness and friction and wear properties of SiCp/HEA composites were tested,and the effects of different interfacial layers on the phase structure,microstructure and properties of the composites were investigated.The results are as follows.XRD results show that for the untreated SiCp/HEA composite materia,diffusion of C and Si atoms into high entropy alloy matrix to form carbides and silcdes,at the same time,the FCC phase in the composite material disappears.Compared with HEA,the compressive yield strength were improved whereas the elongation were reduced,and the crack didn't deflected at the interface.This is mainly attributed to the existence of SiO2 interface layer in oxidized SiCp/HEA composites,which hinders the diffusion of C and Si atoms.However,there are a large number of pores in the composite structure,resulting in a significant decrease in its comprehensive mechanical properties,and the crack directly enters the SiCp after passing through the interface.According to the He-Hutchinson model theory,the interface bonding strength of the two composite materials may be too high,and thus cannot to toughening effect.Subsequently,copper-coated and cobalt-coated SiCp/HEA composites were prepared by electroless plating.Due to the existence of Cu and Co interface layer,the diffusion of C and Si atoms to HEA matrix was inhibited,and the SiC reinforced phase played a reinforcing role.However,compared with HEA,the toughness of copper-plated SiCp/HEA composite is similar to that of HEA,while the toughness of cobalt-plated SiCp/HEA composite decreases slightly,indicating that the interface fails to play a good toughening effect.Therefore,the interface optimization design of SiCp/HEA composite was carried out.The surface of SiCp was coated with cobalt twice,three times and copper after cobalt plating,and the corresponding SiCp/HEA composite was prepared.It was found that with the increase of coating thickness,the inhibition of C and Si atomic diffusion was significantly improved,and the fracture strain was also increased,indicating that the toughening effect of the two interfaces was improved.Compared with HEA,the fracture strain of copper-plated SiCp/HEA composite after cobalt plating is increased,indicating that the Co-Cu interface can play a better toughening effect.