Preparation,Microstructure And Properties Of W-Si-C Composites

Tungsten has many excellent properties,such as high melting point,high thermal conductivity,high sputtering threshold,high hardness,low tritium retention and good neutron irradiation resistance.It is considered to be the most ideal plasma facing material in nuclear fusion reactor.However,the poor sintering activity,low temperature brittleness and low mechanical properties of tungsten limit its application in the field of nuclear fusion.The less slip system of tungsten and the segregation of impurities at the grain boundary lead to the brittleness of tungsten.In this paper,aiming at the problems of high brittleness and low strength,a small amount of second phase SiC was introduced into tungsten matrix by high energy ball milling.The influence of SiC addition and sintering temperature on the densification,microstructure evolution and mechanical properties of the materials was studied.The strengthening mechanism of W-Si-C composite and the sintering activation energy were calculated by using dynamics.The major conclusions of this paper are as follows:（1）The density and mechanical properties of tungsten can be improved by adding a certain amount of SiC.The density,tensile strength and hardness of tungsten materials first increase and then decrease with the increase of SiC content.W-1.0 wt.%SiC composites has the highest density and properties among W-0.5 wt.%SiC,W-1.0 wt.%SiC,W-1.5 wt.%SiC and W-2.0 wt.%SiC.When the sintering temperature is up to 1880℃,the relative density,tensile strength and hardness of the material reach the maximum,which are 99.4%,431 MPa and 697 HV_0.2,respectively.（2）The existence of impurity oxygen in grain boundary is an important factor for tungsten embrittlement.The added SiC will react with oxygen in tungsten to form SiO₂.The sintering activation energy of W-1.0wt.%SiC composite is 398 k J·mol^-1,which is lower than that of pure W(484 k J·mol^-1),and the densification rate is accelerated.（3）W/W₂C/SiO₂ three-phase does not form interface defects,SiO₂exists in amorphous form,and there is an interface transition zone at the interface between W and W₂C to improve the interface strength.The fracture mode of W-Si-C composite is the mixed mode of transgranular fracture and intergranular fracture.There are 46 figures,4 tables,121 references.