Study On Microstructure And Properties Of Cu-Cr-Co-Re Alloy After Solid Solution And Aging

As copper alloys have good electrical properties,thermal conduction and antifatigue resistance properties,they are widely used in the integrated circuit lead frame materials,copper bush of continuous casting mould,and contact wire of high-speed electrified railway.However,with increasingly stringent application environments in the fields of electronics,aerospace,and metallurgy,higher requirements have been placed on the performance of copper alloys.Therefore,it is of great significance to optimize the alloy composition and heat treatment process and develop excellent performance copper alloy materials.In this paper,the Cu-Cr-Co-RE alloy is prepared by smelting in a 0.5t medium frequency electromagnetic induction furnace in non-vacuum condition.The cast Cu-Cr-Co-RE alloy were subjected to the strengthening of solid solution and aging treatment.By comparing the properties of as-cast,solution treated and aged alloys,the effects of different aging temperatures and time on copper alloy conductivity,hardness testing and metallographic structure were analyzed.With the help of the MMW-1friction and wear testing machine,scanning electron microscope,energy dispersive spectrometer and XRD diffractometer,friction and wear tests under different loads and 800?molten salt corrosion tests under different corrosion media were performed.The main results of the research are listed below:?1?950?solid solution 1h/water-cooled,450?aging 2h/water-cooled,Cu-Cr-Co-RE alloy can obtain better hardness,electrical conductivity and so on.The hardness of the alloy under this condition is 195HBW,the alloy conductivity reaches 72%IACS.?2?The microstructure analysis of the Cu-Cr-Co-RE alloy shows:a small amount of Cr is added to the copper alloy.After solid solution and aging treatment,fine-distributed precipitation precipitates and solid solution transformed twins are obtained,which improves the mechanical properties of copper alloy.And due to the presence of twin structure has little effect on the electrical conductivity of the alloy,copper alloy still has a higher electrical conductivity.Adding a small amount of Co,RE element,the alloying elements form an intermetallic compound with Cu matrix,dislocation movement is hindered,and the alloy grain is refined.?3?Under different loading conditions,the friction coefficient of Cu alloy after solution and aging treatment floats around 0.2,and the wear loss is also below 3.0 mg.Compared with the as-cast alloy,it is greatly reduced the abrasive particles and oxides in wear debris furrow.And the wear resistance of alloy also has been improved.The main wear mechanism of the alloy is grinding wear and adhesive wear.With the increase of the load,The friction coefficient,mass wear and the adhesive wear of the copper alloy were also increased.?4?Due to the chlorination-oxidation coexistence cycle mechanism,The as-cast copper alloy in the mixed chloride molten salt at 800°C was caused more severe corrosion than the mixed sulfuric acid molten salt.Because of the chloride volatilization during the corrosion process,The surface oxide film was loosed and occured peeling.When the alloy is mixed in the molten salt of sulfuric acid,there is a uniform second phase?Na₂Cr O₄?and a Cr₂O₃ oxide layer is formed on the surface,which reduces the corrosion rate of the alloy.The solid solution aging treatment of the alloy,due to the precipitation of the second phase?Cu Co,Cr Co,Co Cr Cu?in the heat treatment process,the alloy can effectively inhibit the diffusion oxidation of the alloy elements and reduce the corrosion rate of the alloy to a certain extent.