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.

Interaction of radiation-induced defects with tungsten grain boundaries at across scales: a short review

As promising candidates for plasma-facing materials,tungsten-based materials suffer the irradiation of high-energy neutrons in addition to the hydrogen isotopes and helium irradiation and the high-thermal flux.Radiation-produced defects,e.g.self-interstitial atoms(SIAs)and vacancies(Vs),can induce the hardening and embrittlement of tungsten,meanwhile enhancing the retention of hydrogen isotopes and helium in tungsten.Reducing the grain size of materials to introduce a high density of defect sinks,e.g.,grain boundaries(GBs)prevalent in nano-/ultrafine-crystalline materials,was demonstrated to be an effective approach for mitigating irradiation damage in tungsten.In this paper,we reviewed the theoretical advances in exploring radiation-resistance of nano-structured tungsten at across scales.It was concentrated on the results of molecular dynamics,molecular statics,and the object kinetic Monte Carlo simulations on the fundamental interaction of the radiation-created Vs and SIAs with the GB.These mechanisms include GB-promoted V/SIA migration and SIA-V recombination,interstitial-emission induced annihilation,coupling of the V migration close to the GB with the SIA motion within the GB,and interstitial reflection by the locally dense GB structure.We proposed the remaining scientific issues on the defect-GB interactions at across scales and their relation to experimental observations.We prospected the possible trends for simulating the radiation damage accumulation and healing processes in nano-structured tungsten in terms of the development of the across-scale computational techniques and efficiency of the GB-enhanced tolerance of tungsten to irradiation under complex in-service conditions.