Fabrication And Properties Of Fine-grain Tungsten Alloy

In this paper,high strength/toughness tungsten alloys were prepared by powder metallurgy combined with the basic principles of grain boundary purification and strengthening.The bulk W-0.5%wtZrC(WZC)alloy meeting the engineering application was prepared by the above method and the bulk WZC alloy blank prepared by the traditional sintering method was subjected to high-temperature plastic deformation by using the "top-down" hot rolling process,so as to realize the dynamic recrystallization control and achieve the purpose of further densification and fine crystallization.By adjusting the rolling passes and rolling force,plates with different rolling deformation(46%,69%,77%and 96%)were successfully prepared.The results show that when the rolling deformation is about?69%,the ductile-brittle transition temperature of the W-based alloy is?100? and the mechanical properties are also the best.The previous studies have shown that the fine grain and ultra-fine grain(UFG,100?500 nm)materials with high grain boundary(GB)fraction can improve the radiation tolerance by introducing a large number of GBs into the defect well.Based on the analysis of the dispersion and redissolution of nanoparticles,a reasonable strategy for preparing high stability tungsten materials by particle pinning and solute resistance is proposed.An ultra-fine grained W-0.5wt%ZrC-3wt%Re(WZCR)alloy with an average grain size of 400 nm was prepared by bottom-up powder metallurgy method combining high-energy planetary ball milling and discharge plasma sintering(SPS).The recrystallization and grain growth behavior were studied by isochronous heat treatment experiments.In addition,the effects of Re and nano ZrC particles on the thermal stability and mechanical properties of the ultrafine WZCR alloy were studied by Vickers microhardness test and microstructure analysis.During the service of the first wall material of the fusion reactor,in addition to the serious lattice atom dislocation damage caused by high-energy neutron irradiation,the helium with a concentration of 10?15 appm He/dpa was produced during the fusion reaction.He is easy to diffuse into the material and aggregate to form helium bubbles,resulting in the reduction of material swelling,foaming,hardening,embrittlement,creep and fatigue.This is the helium embrittlement effect.For the high-performance tungsten alloy we prepared before,its anti-He ion irradiation ability is also very important.Therefore,we selected the WZC alloy with 69%rolling deformation for He ion-irradiation research.The results show that under the irradiation dose of 2×1016 ions/cm2 He ion,the coherent and semi-coherent interfaces formed by ZrC particles and W matrix in WZC alloy,and the W grain boundary formed by rolling has an obvious annihilation effect on the irradiation defects(dislocation rings).But the irradiation dose increased to 2×1017 ions/cm2,although some irradiation defects can be annihilated at the grain boundary and phase boundary,more dislocation rings produced by irradiation appear at the grain boundary and in the crystal inside.Positron annihilation spectroscopy shows that more vacancy type defects will appear in the irradiation damage region of the material under a higher dose irradiation environment.In order to further study the anti-He ion irradiation properties of ultrafine-grained materials,the effect of plasma irradiation conditions on the microstructure of materials was discussed,so as to further study the interaction between high crystal boundary and irradiation defects.WZCR alloy was also irradiated with He ion at a dose of 1×1017 ions/cm2.The experimental results show that dislocation rings and micro helium bubbles are produced in the whole irradiation region of WZCR material,but it can still be seen that the high crystal boundary and the second phase interface in ultrafine grains are still important obstacles to the diffusion of He bubbles and increase the radiation resistance.Although there are many results on the effect of He ion irradiation on the properties of tungsten-based materials,they are basically based on the observation of helium bubbles and dislocation movement after irradiation.There is little research on the diffusion dynamics of helium atoms before helium bubble nucleation in tungsten.In Chapter 6,the author prepared helium containing nanocrystalline tungsten films by magnetron sputtering and He with uniform distribution is successfully introduced into the tungsten film.The diffusion mode of He in the tungsten film at low temperature(500 K)is revealed by internal friction technology.The results show that the lowtemperature diffusion of He in Nanocrystalline Tungsten is the long-range diffusion of helium single atom,the diffusion activation energy is 0.42 eV,and the internal friction peak is a typical relaxation internal friction peak.Thermal desorption spectrometer(TDS)reveals that the release peak of he is caused by the desorption of a single He atom near the surface of tungsten at 500-650 K,and the desorption activation energy is 3.19 eV.In Chapter 6,the author prepared pure tungsten nanocrystalline films by magnetron sputtering technology.How to further refine the grains of tungsten films and further enhance their anti irradiation effect.Therefore,in the appendix,this paper studied the preparation of ODS strengthened metal films by magnetron sputtering technology.The results show that the prepared ODS metal films have finer grains and stronger hardness,It is a fast and effective material reinforcement method.The optimum rolling deformation of tungsten base alloy was explored,and the preparation process of fine-grained tungsten material was optimized.Through the research on the damage mechanism of tungsten material during He plasma irradiation,the research in the field of low energy and high beam density ion irradiation is enriched,which has important and long-term significance for the research and development of tungsten base material in the field of fusion in the future.