【作者】 袁悦；

【导师】 刘伟； 罗广南；

【作者基本信息】 清华大学 ， 材料科学与工程， 2013， 博士

【摘要】 钨材料作为聚变堆装置中面对等离子体材料（PFMs）的重要候选材料，其在高热/粒子流作用下的损伤行为，不仅关系到材料的使用寿命，还会影响等离子的稳定性及装置的安全性，因此研究钨材料在高热/粒子流作用下的损伤行为，具有重要的科学价值及工程意义。本文利用高热负荷设备GLADIS及高能电子束设备JUDITH1，模拟聚变堆中典型的高热负荷及粒子辐照条件，对钨材料的损伤行为规律及机理进行了研究。通过对钨在垂直位移模式（VDE）高热负荷作用下的再结晶及晶粒长大行为的研究表明，高热负荷作用下钨的再结晶温度显著升高、再结晶过程明显加快、再结晶晶粒尺寸明显细化。随着最高表面温度升高，钨的再结晶晶粒尺寸增大，抗拉强度降低，抗热冲击性能下降，在边界局域模（ELM）循环热冲击作用下易发生表面开裂损伤。去除表面应力或提高基底温度至韧脆转变温度以上，可以有效改善再结晶钨的抗热冲击性能，避免/缓解表面开裂损伤。当基底温度较高时，粗大的再结晶晶粒在ELM循环热冲击作用下发生塑性变形的同时还伴有动态再结晶，最终形成粗糙的表面形态及细小的动态再结晶组织，使得表面硬度有所升高，性能得到了一定的恢复。通过对钨在VDE高热负荷作用下熔化刻蚀行为的研究表明，熔体运动及再分布造成了材料的严重损伤，熔体中气泡的沸腾引起了熔滴的溅射，并导致熔体冷却后形成了疏松多孔的凝固组织。通过对氧化镧掺杂钨（W-1wt%La₂O₃）熔化行为的研究表明，La₂O₃的加入改变了熔体的运动规律，抑制了熔体中的气泡沸腾。通过检测蒸气的化学成分，分析凝固组织的显微结构特征，揭示了钨熔体中气泡沸腾的机理，并深入分析了第二相La₂O₃对气泡沸腾的抑制机理。针对钨的熔化再凝固组织，对其在高热流He粒子辐照过程中的表面损伤行为进行了研究，实验结果表明，随着最高表面温度及粒子注量的增大，表面损伤深度不断增加，但小于未熔化表面的损伤深度；表面损伤形态由气泡状结构不断演变为孔洞或绒毛状结构，且损伤形态与晶粒的晶体取向有着密切的关系。更多还原

【Abstract】 Tungsten （W） materials are considered as most promising candidates forplasma-facing materials （PFMs） in future nuclear fusion devices. The damage behaviorsof tungsten materials under high heat/particle fluxes are of serious concerns not only tothe lifetime of PFMs, but also to the plasma operations and device safety. Therefore, thestudy of damage and erosion of tungsten materials under high heat/particle loads hasimportant scientific value and engineering significance. In this research, high heat flux（HHF） facility GLADIS and electron beam facility JUDITH1are used to investigatethe damage behaviors and underlying mechanisms of tungsten materials under fusionrelevant high heat flux and irradiation conditions.The recrystallization and grain growth behavior of rolled W under verticaldisplacement events （VDEs） heat loads has been studied. We observe that HHF cansignificantly increase the recrystallization temperature, reduce the time required forrecrystallization and refine the recrystallized grains. With increasing peak temperatures,the recrystallized grains grow bigger and the corresponding tensile strengths decrease.Furthermore, cyclic edge localized modes （ELMs） thermal shock tests have beenperformed on the recrystallized W. It turns out that the recrystallized W has bad thermalshock resistance. Electro-polishing and elevated base temperature （above theductile-brittle transition temperature） are found to be effective in promoting the thermalshock resistance and hence suppressing/retarding the surface cracking. Besides, theplastic deformation of recrystallized grains occurs under the cyclic thermal shocks.When the base temperature is elevated, the dynamic recrystallization （DRX） is observed,resulting in rough surface and refined DRX grains which lead to increased surfaceroughness and hardness.In addition, the melting behavior of W under VDE-like heat loads has beeninvestigated. Melt layer motion and redistribution results in severe erosion of thematerials. Bubble boiling in the melt layer induces melt layer ejection and result inporous re-solidified structure. For comparison, the melting tests of W-1wt%La₂O₃havebeen also carried out. The addition of La₂O₃particles notably affects the melt layermotion and suppress the bubble boiling. Detailed characteristics of melt layer structure are analyzed. Evaporation/boiling sources are indirectly studied with aid of vapordeposition/collection. Based on the experimental results, the possible underlyingmechanisms of bubble formation in W and bubble suppression in W-1wt%La₂O₃arediscussed and basic melting and boiling process under high heat loads of the twotungsten grades are tentatively drawn. Thereafter, the molten and re-solidified W isexposed to high heat flux helium neutral beams. With increasing peak temperature andhelium fluence, the damage depth of the molten surface increases, but is still lower thanthe non-molten surface. Blisters are observed on the molten surface, and evolve intoporous or coral-like structure with worsening irradiation conditions. The surfacemorphologies exhibit strong dependence on the re-solidified grain orientations.更多还原