Microstructure And Properties Of AlFeCoCrNi/Cu High-entropy Alloy/Cu Composites Fabricated By Spark Plasma Sintering

Copper-based composites have been widely used in aerospace,automobile,electronics and other fields due to their excellent comprehensive properties.However,currently used copper-based composites generally have the weaknesses of poor bonding between the reinforcement and Cu matrix,low strength and hardness,which greatly limits their applications.Therefore,it is very important to optimize the bonding interface between reinforcement and Cu matrix and improve the strength of composites.In addition,as a new alloy with high strength and hardness,AlFeCoCrNi high-entropy alloy(HEA)can be used as reinforcement which improved the performance of Cu matrix composites.In this paper,heat treatment and hot deformation have been first condueted in the vacuum tube furnace and hot extruder for AlFeCrCoNi/Cu composites were prepared by spark plasma sintering(SPS).To examine the phase identification of HEA powder and microstructures of samples,the X-ray diffraction,scanning electron microscope and energy dispersive spectrometer were used.Finally,the mechanical properties of the composites are measured by microhardness tester and universal testing machine.The conclusions are drawn as follows.The AlFeCoCrNi/Cu composite were sintered in a spark plasma sintering furnacr at 850? with sintering rate of 50?/min.The Cu matrix composite with 20 vol % AlFeCoCrNi has a compressive yield strength of 239 MPa,a relative density of 96.5%,and good plasticity.Due to the mutual diffusion between the reinforcement and the Cu matrix during sintering process,Al and Ni diffuse from the reinforcement to the matrix,and Cu diffuse into the reinforcement,which formed a diffusion layer with a certain thickness between the reinforcement and the matrix.When the annealing condition of Cu matrix composite is 850? for 2h,the Cu matrix can diffuse to the central of the reinforcement.The compressive yield strength of AlFeCoCrNi 20vol% Cu matrix composites is 322 MPa and the relative density is 96.9%.The increase of annealing time has little effect on its properties.Compared with the samples before annealing,a large number of Cu-rich phases mainly composed of Cu,Al and Ni appear in the reinforcement.With the increasing annealing temperature,the thickness of diffusion layer increases and enhance the precipitation of Cu-rich phase.Bsides,Cu-rich phase aggregate toward to the particle center of the reinforcement particles.When the AlFeCoCrNi 10vol% Cu matrix composite was fabricated by hot extruded at 850?,its mechanical properties are obviously enhanced with the increase of hot extrusion and holding time.When the holding time reach 6h,tensile yield strength,tensile strength,elongation and relative density of compoistes are 318.8MPa,375.6MPa,10.2% and 99.2%,respectively.Compared with the sample without extrusion,its plasticity has decreased to some extent,its strength and density are obviously improved.When the composite fractures,the crack starts from the junction of the diffusion layer and the matrix.As the crack expands,the reinforcing particles debonded and caused the material to fracture.