Design,Preparation And Performance Evaluation Of W-Cu Functionally Graded Materials For Fusion Reactors

W-Cu functionally graded material（W-Cu FGM）are used in the plasma-facing components due to the advantages of high melting point,low sputtering rate,good thermal conductivity,non-reaction with H of W and the excellent thermal conductivity of Cu,to mitigate the thermal stress caused by the large difference in the coefficient of thermal expansion between plasma facing material of W and heat sink material of Cu.In nuclear fusion reactor,the W-Cu FGM expose to high heat loads,which seriously affects the lifetime of the component.Considering the safety life of W-Cu FGM for fusion reactor application under high thermal load,the structure design,preparation and service behavior evaluation of W-Cu FGM were researched in this dissertation.（1）The graded structure of W-Cu FGM has obvious influence on the interface stress under high temperature service,finite element analysis method（ANSYS Workbench18.1）was employed to simulate and analyze the thermal stress of W-Cu FGM under steady thermal load.The layers and Cu component distribution index in layered W-Cu FGM were optimized.It was found that when the Cu component distribution index is 1 and the layer number of 4,a best stress relief effect is obtained,which is 46.7%lower than that of the single layer.When layer number is 4,the best relief effect was obtained at the Cu component distribution index of 1.6.The temperature and stress of the W-Cu gradient module during thermal shock were simulated.The results show that the heat flow only concentrates on the surface of the W layer,and the influence on the temperature of the heat sink material is not significant.（2）The transient thermal shock test of W-Cu FGM was carried out and its damage behavior was analyzed.W-10Cu composite powder prepared by electroless plating and superfine W powder with particle size of 100～200 nm prepared by the solution combustion synthesis and hydrogen reduction method were used as raw materials.Green W/W-10Cu/W graded parts was obtained by laminated pressing.And W/W-10Cu/W graded composites were prepared by sintering in H₂ at 1550℃for 90 min.It was found that the surface roughness of the sample increases after laser thermal shock when used W layer as the irradiated surface,and at the same time,it begins to melt and the microhardness decreases.After thermal shock,longitudinal cracks appear in the pure W layer and gradually terminate when they extend to the W-10Cu layer.（3）The cyclic thermal shock test of W-Cu FGM was carried out and its damage behavior was analyzed.W-10Cu composite powder prepared by electroless plating process and Cu powder were used as raw materials.The gradient W-Cu material of W-10Cu/W-20Cu/W-30Cu were obtained by laminated pressing and sintering in H₂atmosphere.The cyclic thermal shock test was carried out the prepared W-Cu FGM.The results show that the failure behaviors of W-Cu FGM during thermal shock mainly include Cu exudation,pores and cracks.After 200 times of thermal shocks at 1000℃,the thermal conductivity of the samples at room temperature decreases by 20.60%,and the thermal expansion coefficient of the samples decreases by 2.94%.In addition,the thermal shock resistance of W-Cu composites is related to the mechanical properties.The higher contents of Cu in W-Cu composites,the greater G_IG and the better thermal shock resistance were showed.