Research On Irradation Damage And Heat Shock Behavior Of Rare Earth Oxide Strengthened Tungsten Composites

Tungsten and its composites exhibit the advantages of high melting point,high thermal conductivity,and low sputtering rate.Tungsten is considered the most promising plasma facing materials.However,under the condition of fusion service environment,tungsten and its composites suffer up to 14 Me V neutron irradiation,high heat load,low energy and high flux(up to 10²²–10²⁴m^-2s^-1)hydrogen-helium plasma-irradiation damage,resulting in performance degradation and shortened service time seriously affecting the safety and reliability of fusion devices.In this study,W-Y₂O₃ composite material were prepared by wet chemical method and rolling method.Select commercially pure tungsten for the comparative sample,the rolling ratio of the two materials was 50%.Study the surface structural changes of materials after helium ion irradiation,research the influence of different temperature annealing on the surface morphology evolution of materials after helium ion irradiation,analysis rare-earth oxide doping material structural changes.In addition,the laser thermal shock and the damage behavior of the material after helium ion irradiation were studied,discussed the second phase damage behavior.The main results of the study are as follows:(1)For the helium ions irradiation samples,the irradiation area was a circle with a diameter of 10 mm,a boundary exists in the irradiation,affected,and unaffected areas.In the unaffected area,the Y₂O₃ particles were obviously cracked.In the affected area,similar to the irradiation area,the damage of the tungsten grain showed different orientations.In the irradiation area,the damage morphology after helium ion irradiation shows remarkable differences caused by different grain orientations.In addition,the fuzz structure at the phase interface is denser and smaller,the materials surface damage due disappears after annealing at a certain temperature,and the phase interface is favorable for the helium bubble formation at a deeper position from the tungsten substrate surface.(2)To reduce the impact of the interface on the irradiation damage of the material,we processed complete recrystallization annealing of the material.After helium ions irradiation,a denser and smaller fuzz structure is produced at the phase interface.Helium bubbles were widely spread in the near-surface layer of the pure tungsten materials,in contrast,the number of helium bubbles in the tungsten grains of the W-Y₂O₃ composite material was remarkably reduced.After helium ion irradiation,the vacancy concentration at the depths of a few nanometers in the near-surface of the W-Y₂O₃ composite material was lower than that of the pure tungsten.Therefore,the addition of the second phase Y₂O₃improves the irradiation resistance of the material.(3)The synergistic effect of laser thermal shock and helium ion irradiation on the materials was studied.Compared with pure tungsten,W–Y₂O₃ composite material have higher resistance to laser thermal shock.Additionally,cracks in these materials were generated and propagated easily along the direction of grain elongation.After helium ion irradiation,the cracking caused by laser thermal shock was dominated by intergranular cracks.In the obvious cracks,fuzz structures were observed inside the cracks after helium ion irradiation and damaged the material in the depth direction.In addition,grain orientation resistance to helium ion irradiation damage is more significant than that to increasing grain boundary density.At last,after helium ion irradiation,several helium bubbles were observed in the tungsten matrix,fuzz structure,and Y₂O₃ particles.The helium bubbles were polyhedral rather than spherical.