Research On Microstructure And Properties Of Graphene Reinforced Copper Matrix Composites

Copper has excellent conductivity,thermal conductivity and processing properties,which has been widely used in aerospace,marine engineering?electronics and automobile industries.However,The characteristics of high plasticity and low strength make its application becoming limited by a large scale.The traditional method of adding carbon fiber or carbon nanotubes can obtain good effect,which could effectively guarantee the high thermally conductive and wear-resisting performance,while there are such problems as poor mechanical properties and difficult preparation process.Therefore,It is of great significance to develop new types of reinforcement to further explore the application potential of copper.Graphene has high thermal conductivity,strength and conductive,which has significant advantages to develop copper matrix composites.However,graphene has a larger specific surface area which is prone to get together in the preparation process.Besides.It also has poor wettability with copper.In this paper,titanium powder and chromium powder were added to the graphene reinforced copper matrix composites to improve their comprehensive properties.Copper powder and graphene were mixed by ultrasonic dispersing and high-energy ball milling,and then discharge plasma sintering method was used to prepare graphene reinforced copper matrix composites.The structure and properties of graphene copper-matrix composites were analyzed.The conclusion is as follows:(1)After ultrasonic and ball milling,the composite powders were flat in the scanning electron microscope.The graphene was partially rejoined in the copper powder,which was not oxidized during the process of mixing powder by XRD.(2)The copper matrix of graphene reinforced copper matrix composites added by titanium is recrystallized and accompanied by the formation of twin structures.With the increase of sintering temperature,the grain size in the composite material is increasing,while the porosity and other defects are decreased correspondingly.As the temperature ranges from 750? to 900 ?,density and hardness values of the composite material is on the rise,while whose conductivity decreases.Under the sintering temperature of 750 ?,the conductivity of composites reaches highest at 56.8%IACS.Under the sintering temperature of 900 ?,the density of the composite reaches highest value of 8.54 g/cm3,which is nearly to the pure copper(8.51 g/cm3)level.Brinell hardness value reaches at 66.4HB,which is increased by 42.5%compared to pure copper(46.6HB).(3)With the sintering pressure increasing,the matrix of graphene reinforced copper matrix composites added by titanium obviously appeared decreasing on the overall grain size.The grain refinement can significantly improve the strength of the composites.As the pressure ranges from 5MPa to 30MPa,the density of composite material ranges from4.47g/cm3 to 8.54g/cm3,which increases 391.1%,and the hardness of composite material ranges from 33.4HB to 66.4HB,which increases 98.8%,.The conductivity initially increses and then decreases,Which reaches the highest at 51.2%IACS under the sintering pressure of 25MPa.(4)As the temperature ranges from 750? to 900 ?,density and hardness values of the composite material initially increase then deseaces and finally increases.while the conductivity of the composite material initially keep unchanged then decreases.When the sintering temprature ranges from 750? to 850?,the conductivity of the composite material is 50%IACS;graphene reinforced copper matrix composites added by chromium powder reaches the highest at 8.45g/cm3When the sintering temprature is 900?;Brinell hardness value reaches at 54.8HB under the sintering temparature of 800?.In addition,the metallographic structure of composite materials gradually decreases with the increase of sintering pressure.When the sintering pressure rises from 15MPa to 35MPa,the density of composite material ranges from7.84g/cm3 to 8.43g/cm3,which increases 7.53%,and the hardness of composite material ranges from 43.4HB to 57.3HB,which increases 32%,The conductivity initially decreases and then increses,Which reaches the highest at44.5%IACS under the sintering pressure of 35MPa.(5)As the addition of graphene increased from 0.1%to 0.5%,the density of graphene reinforced copper matrix composites increased at first and then slowly decreased.The conductivity decreased from 70.7%to 66.9%,which only decreases slightly.The hardness initially increased and then slowly decreased,the hardness of the graphene reinforced copper matrix composites reachs 51.4 when the content of graphene is 0.3%.The density of copper/titanium composites also increases first and then decreases with the increase of the content of graphene.The conductivity initially decreases,then rises,and finally decreases.When 0.1%graphene is added,the conductivity of copper/titanium composites decreases to 55.3%IACS.When the amount of graphene is 0.3%,the conductivity of the graphene increases to 59.6%IACS.When the amount of graphene is 0.5%,the conductivity decreases slightly to 50.4%IACS.The variation of hardness with the amount of graphene shows the opposite trend of conductivity,which reachs a maximum value of 63.7HB at 0.5%of graphene.The density of copper/Cr composites decreases with the increase of graphene content.The conductivity is decreasing with the increase of the added quantity,When the addition of graphene increases from 0 to 0.5%,the conductivity decreases from 66.6%IACS to 41.3%IACS.Hardness is also decreasing,and when graphene is added from 0 to 0.5%,hardness decreases from 61.8HB to 55HB.