Preparation And Properties Of Plasma Facing W-Nb Composites

Tungsten and tungsten alloys have been considered to be the best candidate for the first wall of the plasma material,because of their high melting point,low sputtering,high thermal conductivity and low deuterium retention,etc.However,those problems,such as low temperature brittleness,high ductile and brittle transition temperature and radiation brittleness,limit their application in fusion reactors.Micro-alloying is an effective method to improve the comprehensive properties of tungsten matrix composites.In this paper,Nb,Ti alloy elements modified W-based composites by mechanical milling,and SPS sintering was used to prepare the W-based composites.The effects of Nb contents and milling time on the microstructure and properties of W matrix composites were studied,and the collaborative doping of Nb and Ti,collaborative doping of Nb and TiC on the microstructure and properties of W matrix composites were also studied.The following conclusions could be drawn:(1)Nb alloy element can significantly improve the relative density and thermal conductivity of W–TiC composites,and Nb doping can significantly improve the high temperature tensile strength of W–TiC composite.(2)A small amount of Nb and Ti doped W material,which can effectively reduce the total D2 retention,can improve the W–Nb/Ti composite deuterium radiation resistance.The porosity of W-Ti/Nb composites increased with the Ti content increased.The microhardness of W matrix composites decreased from 697.0 HV to 608.9 HV with the Ti content increased.The maximum tensile strength(410.53 MPa)was detected in the W–4wt%Ti–1wt%Nb composite at 600 ?.A Ti(X)W(1-X)solid solution was formed during sintering.(3)The crystalline size of the W–Nb mixture powders decreased,whereas the lattice strain and dislocation density increased as the milling time increased.The W–Nb compositesmilled for 25 h exhibited the lowest porosity,and the Nb-rich phase became small and uniformly distributed in the tungsten grains and boundaries of this composite.The W–Nb composites milled for 25 h exhibited the optimal deuterium irradiation resistance.(4)The particles size decreased as Nb content increased.The Nb alloy element had significant effect in promoting W-based materials densification.The micro-hardness increased as Nb content increased,which can be ascribed to fine grain and low porosity.Total D retention increased as Nb content increased,excessive Nb-doped W-based materials were harmful to deuterium irradiation.