Mechanical properties and thermal shock resistance of tungsten alloys strengthened by laser fragmentation-processed zirconium carbide nanoparticles

Zirconium carbide(ZrC)nanoparticles with an average size of 5.6 nm were synthesized through laser fragmentation(LF)from as-received 20-60 nm ZrC particles,and LF-ZrC nanoparticle dispersion-strengthened tungsten(LF-WZC)samples were fabricated by spark plasma sintering method.The average grain size of LF-WZC is 1.91μm and most ZrC particles in LF-WZC are smaller than 10 nm.LF-WZC exhibits finer grain size,higher yield strength and hardness but lower ductility as compared with W-ZrC samples using as-received ZrC(WZC).The results showed that finer ZrC nanoparticles dispersed in tungsten can enhance the strength by hindering the motion of dislocations,but they may also introduce stress concentra-tion and thus reduce the ductility.The thermal shock resistance of the WZC and LF-WZC samples was investigated using an electron beam device.The LF-WZC sample also exhibits a higher cracking threshold(0.33-0.44 GW·m^(−2))than WZC(0.22-0.33 GW·m^(−2))at room temperature.The enhanced thermal shock resistance of LF-WZC could be attributed to its high yield strength.

Evaluation of tungsten interatomic potentials for radiation damage simulations

The structure and properties of materials under neutron irradiation are an important basis in future fusion reactors.In the absence of fusion neutron sources for irradiation experiments,it is increasingly important and urgent to carry out neutron irradiation simulations on fusion reactor materials and then establish complete databases of defect properties and collisional cascades,where the first and foremost step is to select suitable interatomic potentials for atomistic-level simulations.In this work,six typic interatomic potentials for tungsten(W)are evaluated and reviewed systematically for radiation damage simulations.The relative lattice stability and elastic constants of bulk W are considered first with those potentials;then,the properties of point defects and defect clusters at interstitial sites and vacancies are obtained by molecular statics/dynam-ics simulations.The formation energies of interstitial/vacancy clusters,1/2<111>and<100>dislocation loops in W and the threshold displacement energies along different directions are also determined.In addition,the extended defects are further investigated,such as free surfaces and the energy profiles of 1/2<111>{110}and 1/2<111>{112}stacking faults.The current results provide a reference for selecting W potentials to simulate the radiation damage.

Preface to the special issue on metallic materials for fusion applications

Tungsten as a refractory metal shows attractive and promising thermal properties at high temperatures such as the high melting point and the high thermal conductivity.In a nuclear fusion environment,tungsten is a favorable material because of its thermal properties as well as the good resistance to particle erosion,neutron irradiation,and tritium retention.The major concern using a tungsten wall is the radiative cooling of fusion plasma by tungsten impurities.