Study On Preparation And Microstructure And Properties Of Layered Heterogeneous Copper Matrix Composites

Beryllium copper(Cu-Be)alloy has the characteristics of high strength,high hardness,good wear resistance,excellent fatigue resistance,etc.It is widely used in aerospace,automotive rail,military industry and other fields.The high-content beryllium copper(Cu-Be)alloy has a tensile strength of over 1400 MPa after aging,and an elongation of less than 5%,showing a significant reverse relationship between strength and plasticity/toughness,which seriously affects the safety and reliability of alloy service Therefore,it is of great significance to explore a method to improve the strength and toughness of Cu-Be alloy.In this paper,industrial Cu-Be(C17200)and Cu-Zn(C26000)alloys are used as raw materials to prepare Cu-Be/Cu-Zn layered metal matrix composite materials by vacuum hot pressing composite technology.The influence of hot pressing process on the interface microstructure and mechanical properties of layered metal matrix composite was studied.The cold rolling of metal matrix composite was carried out.The thickness and microhardness evolution of metal layer and interface transition layer under different cold rolling reduction rates were explored,and the influence of interface transition layer on the cold rolling deformation behavior of layered metal matrix composite was discussed.Layered metal matrix composites with different thickness ratio of Cu-Be/Cu-Zn(1:1?2:1?5:1)were prepared,and the effect of thickness ratio on the strength,toughness and back stress strengthening of the composites was explored.The main conclusions are as follows:(1)The process parameter of vacuum hot pressing bonding is 780?-30MPa-30 min.The interface of Cu-Be/Cu-Zn layered metal matrix composites is tight,without cracks,holes and other defects under different hot pressing time.The prepared CuBe/Cu-Zn layered metal matrix composites does not exhibit interlayer cracking in the bending performance test.Among them,the layered metal matrix composites with hot pressing for 30 minutes has the highest bending strength,and bending strain;the tensile strength and tensile strain of Cu-Be/Cu-Zn layered metal matrix composites under 30 min hot pressing are 420 MPa and 60.6%,respectively.(2)The Cu-Be/Cu-Zn layered metal matrix composites are cold-rolled at different reduction rates.When the reduction rate is 35%,the deformation is mainly concentrated in the Cu-Zn layer.When the cold rolling reduction rate increases to 80%,a few grains in the Cu-Zn layer show local necking,and the grains in the Cu-Be layer is significantly elongated along the RD direction without necking.When the rolling reduction rate is below 50%,the Cu-Be/Cu-Zn layered metal matrix composite material undergoes inhomogeneous macroscopic deformation.The deformation amount of the Cu-Zn layer in the thickness direction of the sheet is significantly greater than that of the Cu-Be layer and interface transition layer.when the cold rolling reduction rate is 35%,the thickness of the interface transition layer is only reduced by 8.3%,and the inhomogeneous plastic deformation causes the Cu-Be/Cu-Zn interface to change from a flat state to a wavy state.When the reduction rate exceeds 65%,uniform and coordinated deformation occurs in the layered metal matrix composite,and the thickness of each layer basically changes according to the total cold rolling reduction rate.Under different cold rolling reduction rates,the microhardness of the transition layer is the highest,followed by the Cu-Be layer,while the Cu-Zn layer has the lowest microhardness.The reason is that during the cold-rolling deformation of the layered metal matrix composite,the interface transition layer mainly plays the role of coordinated deformation,which is under significant shear stress and results in generating additional back stress strengthening.(3)The microhardness of Cu-Be layer in Cu-Be/Cu-Zn layered metal matrix composites with different layer thickness ratio(1:1?2:1?5:1)is significantly higher than that of Cu-Zn layer in aging state,and the microhardness of Cu-Be layer with layer thickness ratio of 5:1 is more than 200% higher than that of Cu-Zn layer.The strength of layered metal matrix composites with different layer thickness ratio is higher than that of Cu-Zn alloy,and the plasticity is better than that of Cu-Be alloy.With the increase of the layer thickness ratio,the tensile strength and elongation of the composite increase at the same time and the type of tensile fracture of the Cu-Be layer changes from brittle intergranular fracture to quasi cleavage fracture,indicating the plasticity of the Cu-Be layer increases gradually.While the fracture mode of the Cu-Zn layer under different layer thickness ratio is microporous aggregation ductile fracture.With the increase of thickness ratio,the back stress and strain hardening ability of the layered composite materials increase gradually.By introducing the design of configuration compounding,the dislocation dynamic recovery rate of Cu-Be/Cu-Zn layered metal matrix composite materials is significantly lower than that of Cu-Be alloy during plastic deformation.Hence,the strain hardening ability of the materials is significantly improved,which is the main reason for the high strength and toughness of Cu-Be/CuZn layered metal matrix composite.