Performance Of W/Cu Functional Graded Materials Prepared By Hot Pressing

W/Cu functionally graded material?FGM?combines the different excellent properties of W and Cu,and decreases the thermal stress for the big difference of thermal expansion coefficient between W and Cu.It also solves the connection problem due to the great difference of their melting points,and makes W and Cu give full play to their respective intrinsic physical properties.W/Cu FGM combines their advantages and makes up for their shortcomings,which improves the comprehensive properties.Because of the excellent performance,W/Cu FGM is widely used in different fields.Firstly,in this paper the wettability of W and Cu interface is improved by using the simplified W powder pretreatment process.The surface of the W particles is coated with a uniform,complete and dense Cu layer,which improves the bonding strength between W and Cu interface and makes the distribution of W powder more uniform.The effects of W loading,reducing agent concentration and bath temperature on the Cu coating on the surface of W powder particles were studied by field emission scanning electron microscopy and X-ray diffractometer.It is concluded that the optimal process of copper plating is as follows: the loading of W powder is 10g/L,the concentration of formaldehyde HCHO is 20 ml / L,and the temperature of bath is 60 ?.In this paper,the three-layered?W-60vol%Cu/W-40vol%Cu/W-20vol%Cu?W/Cu FGM containing a Cu-network structure was fabricated at different temperatures by hot pressed sintering produced from copper-coated tungsten powders.The effects of different sintering processes on the microstructure and properties of the composites were studied by XRD,SEM and EDX.The results show that the samples prepared at 1065 ? have good comprehensive properties.The relative density is up to 96.1%.The thermal conductivity is up to 204 W?m^-1 K^-1 at normal temperature and 150 W?m^-1 K^-1 at 800 ?.The electrical conductivity is as high as 71.34% IACS.The sample sintered at 1065 ? was heated to 800 ? and water quenched.There was no cracking phenomenon on the quenched sample in the SEM images,reflecting the excellent thermal shock resistance.For W/Cu functional graded materials are widely used in plasma facing materials in the future,the five-layered?W-80vol%Cu/ W-60vol%Cu/ W-40vol%Cu/ W-20vol%Cu/ W-0vol%Cu?W/Cu FGM was designed and fabricated refer to the optimum preparation process of the three-layered W/Cu FGM.The physical properties was also studied,and the results show a low interfacial bonding strength due to a number of porosity defects in the pure W layer.The relative density is as low as 93.6%,and the thermal conductivity is 125 W?m^-1 K^-1 at room temperature and 87 W?m^-1 K^-1 at 800 ?.The electrical conductivity is 45.27% IACS which presents a low level.The thermal shock resistance is pretty poor.