Study On Microstructure And Properties Of Cu-Cr Composites Prepared By Rolling

In the era of rapid development of manufacturing industry,copper matrix composites have broad application prospects due to their advantages of variety,high conductivity,high thermal conductivity and high ductility.Accumulate roll bonding(ARB)is commonly used to prepare metal matrix composites with fine grains and comprehensive excellent properties,which provides an effective new way for the development of high strength and high conductivity copper matrix materials.In this paper,Cu-Cr composites were successfully prepared by the combination of accumulative roll bonding technology and heat treatment process.The microstructure,interface morphology,chemical composition and phase composition of the materials were characterized by OM,TEM,SEM,EDS and XRD.The mechanical properties and electrical conductivity of the materials after accumulative roll bonding were tested by microhardness tester,tensile testing machine and DC double-arm bridge.The main research contents are as follows:The effect of chromium powder addition method on its uniformity was studied.The results showed that the screening method was better,and the distribution of chromium powder in the matrix was further improved by means of cumulative rolling.After adding chromium powder,the grain size of the composite material in the rolling normal direction decreased,and the grain aspect ratio increased from 7.46 to 13.90,which increased by86.32%.After cold rolling and hot rolling,the tensile strength of Cu-Cr composites increased by 8.27% and 6.57% respectively,and the conductivity decreased by 1.37% and8.63% respectively.The effects of rolling passes and preparation process on the microstructure and properties of Cu-Cr composites were studied.The results showed that after the first pass of accumulative roll-bonding,the mechanical bonding between chromium powder and matrix is preliminarily realized,and the grains were elongated along the rolling direction.The dislocation distribution of copper matrix was more uniform and directional than that of the initial state,with a dislocation width of 32.76 nm.After the second pass of accumulative roll bonding,the bonding quality of chromium powder and matrix is improved.After the third pass of accumulative roll bonding,the chromium particles were deformed and “tailing” appeared and their size decreased from 22.30 μm to 17.33 μm.It was found that the grain size increased first and then decreased.The dislocation width decreased to 19.13 nm,which decreased by 41.61%.The tensile strength of Cu-Cr composites prepared by three processes of non-annealing,240 °C×30 min annealing and350 °C×5 min annealing increased by 9.08%,4.42% and 5.37% respectively after three passes of accumulative roll bonding.Among them,the comprehensive properties of Cu-Cr composites after three passes of rolling at 350 °C×5 min were the best in the annealing process,with a tensile strength of 314.88 MPa and a conductivity of 71.83% IACS.The microstructure and properties of Cu-Cr composites by thermal accumulative roll bonding at 450 °C were studied.The results showed that the grain size gradually decreases with the increase of the number of cyclic rolling in the normal direction of rolling,and the elongated grains with clear initial grain boundaries were transformed into fine grains with blurred grain boundaries.After three passes of accumulative roll bonding,the interface bonding quality of the material was better,with a tensile strength of 382.12 MPa and a conductivity of 81.19% IACS.