Damages on pure tungsten irradiated by compression plasma flows

Experimental and simulation studies on damage mechanisms of tungsten and molybdenum under compressed plasma flow irradiation

“…A melting wave is a special surface characteristic induced by the rapid solidification of the molten layer when the mass migration is driven by a force parallel to the surface direction. There were two driving forces for surficial mass migration under CPF irradiation [13]: on the one hand, the molten surface was affected by gravity due to fact that the tungsten and molybdenum were perpendicular to the ground; on the other hand, the molten surface was also affected by the plasma pressure difference because the actual plasma distribution was not completely uniform on the surface. It is generally believed that columnar grains are the common grain organization after directional solidification treatment, formed by heterogeneous nucleation and epitaxial growth.…”

“…When ELMlike thermal shock irradiation is sufficient to melt the material, the re-solidified layer tends to form a columnar grain structure [9][10][11]. A submicron-sized cellular sub-grain structure is also frequently seen on the surface of materials after ELM-like thermal shock irradiation [10,[12][13][14][15][16][17][18][19][20]. However, researchers are not unanimous in their interpretation of the formation of the cellular sub-grain structure.…”

“…Shymanski et al [12] suggested that the separation of light impurities (like carbon or oxygen) in the material before crystallization could lead to the disturbances of free surface and consequent creation of such a structure. Although Qu et al [13] were unable to determine the cause of the formation of the cellular subgrain structure, they suggested that its size might be related to the viscosity of the molten material. After irradiation, macrocracks and micro-cracks appear on the tungsten surface [19,21].…”

“…After irradiation, macrocracks and micro-cracks appear on the tungsten surface [19,21]. Macro-cracks occur due to the intrinsic brittleness of the material, while micro-cracks are related to the melting and resolidification process [13]. Besides the ductile-to-brittle transition temperature (DBTT) of the material [22], the heat flux factor of the thermal shock irradiation [23], the base temperature of the material during irradiation [24,25] and the processing history of the material [26] are the key factors affecting macro-crack generation.…”

“…A pulsed plasma [13,21,29], high-power electron beam [26,30] and strong laser [31,32] are commonly used for the experimental study of ELM-like thermal shocks due to the limitation of the amount of experimental equipment available for large-scale fusion reactions. Previous experiments showed that the materials exhibited similar damage behavior and damage thresholds for different thermal loading techniques [17,33,34], all of which have good reliability in testing the transient thermal shock resistance of materials.…”