Research On The Preparation Technology And Properties Of Nano-WC Reinforced Copper Matrix Composites

High strength and high conductivity copper alloy has been widely used in core electronic devices,extremely large scale integrated circuits,high speed rail transit,new energy vehicles,and other fields,which put forward higher requirements for the performance of high strength and high conductivity C u alloy.In this paper,nano-WC was added to Cu matrix composites as strengthening phase particles.After the composite powder was mixed homogeneity by mechanical alloying method,nano-WC/Cu-based composites were prepared by vacuum sintering,induction melting,arc melting,and hot-pressing sintering.The optimal process was obtained by comparison.The microstructure and structure of the samples were analyzed by means of XRD,SEM,and TEM.The effects of different sintering temperatures on the microstructure,electrical conductivity,strength,and hardness of the composites were studied.The preparation mechanism of nano-WC reinforced C u matrix composites was also explored.The specific conclusions are as follows:(1)After mixing nano-WC powder and pure Cu powder according to the mass ratio of WC : C u= 1: 9,the WC is uniformly dispersed on each Cu particles,which can achieve an excellent mixing result.By comparing the microstructure morphology of the composites prepared by different processes,it can be concluded that the nano-WC/Cu-based composite prepared by vacuum hot-pressing sintering are more compact in structure and simpler in process.Likewise,the WC is uniformly dispersed on the C u matrix without agglomeration and growth.With the increase of sintering temperature,the microstructure of the composites is more uniform and the structure is more compact.(2)In the temperature range of 950 to 1100?,the relative density and electrical conductivity of nano-WC/C u-based composite increased with the increase of hot-pressing sintering temperature.The relative density gradually increases as the sintering temperature rises,whose value is close to the full density when sintering temperature increase to 1075?.The density remains basically invariable when the temperature increases further.The electrical conductivity of the composites sharply increases from 62.5 to 86.2% IACS when sintering temperature increase from 950 to1025°C.With the temperature increases further,the electrical conductivity of the composite gradually changes slowly,and finally reaches about 90% IACS at 1100?.In addition,with the temperature rises from 950 to 1100?,the ultimate tensile strength of the composites gradually increases from 123 to 425 MPa.Furthermore,as the temperature increases,the hardness value increases gradually from 127.5 to 150 HV.But,when the temperature exceeds the melting point of C u(1083?),it is likely that a large amount of liquid phase will be generated during the hot-pressing sintering process,resulting in the liquid being squeezed out and damaging the equipment.Therefore,the sintering temperature in this paper is controlled within 1100?.(3)The high temperature Vickers hardness of nano-WC/Cu-based composite and pure C u gradually decreases as the temperature rises,but the high temperature hardness values of the composites tested at various temperat ures are much higher than that of pure Cu.The high temperature hardness of the composite decreases slowly from 97.9 to 12.7 HV when test temperature increases from room temperature(25?)to 900?,while the high temperature hardness of the pure Cu decreases from 72.4 to3.8 HV.When the temperature increases from 25 to 600?,the high temperature hardness of the composites decreases by 69.05%,and that of pure Cu decreases by84.94%.The high temperature hardness of the composites decreases by 58.09%,and that of pure C u decreases by 65.14% when the temperature increases from 600 to900?.It can be seen that the decrease rate of high temperature hardness of the composites is much lower than that of pure Cu.This is due to the thermal stability of nano-WC particles and the interaction between dislocations and grain boundaries,which reinforced copper matrix composites.This indicates that nano-WC/Cu-based composite have higher service temperature than pure C u.Therefore,adding nano-WC particles into the Cu matrix can significantly improve the high temperature performance of the composites.