​Radiation effects in sapphire crystals (2)

Radiation effects in sapphire crystals (2)

Regarding the nature of the illumination intensity, there are now two explanations for understanding this phenomenon. One is that the nature of these strengthenings should be attributed to the fact that RDs are vacancy-fixed extra centers that reduce the efficiency of dislocation source behavior. The second is through This phenomenon can be explained by the formation of lattice defects that act as barriers to prevent the movement of dislocations on the slip plane.

When RDs impede the motion of dislocations, plastic deformation is also impeded. This results in a rise in the yield point and lattice strengthening. When these impediments are reached, the dislocations wrap around them, but their side wings continue to slip. When The angle between the dislocation wings decreases, and the pressure outside the obstacle rises. As the dislocation passes, the stress rises, and when the above angle reaches a limit value (after this limit value, the dislocation rearranges and continues (moving) dislocations will break away from the obstacle. The stronger the obstacle, the smaller the corresponding limit angle. The irradiation defect groups exist disorderly on the slip surface and have different sizes, so the dislocations often slip from the easiest The path crosses the obstacle. As the applied stress increases, the dislocations continue to move until they cover the entire slip plane and all the obstacle. The additional stress to achieve such movement creates additional initial force for the enhancement of illumination by the non-irradiated crystal Yield point. In general, radiation enhancement of a material is accompanied by a reduction in material ductility due to irradiation embrittlement. Elaboration of the nature of this effect allows the establishment of possible factors that produce it, as well as the establishment of methods to suppress it .

Irradiation embrittlement is often observed in crystals containing blocks. The presence of transmutants, such as noble gases, inside these blocks during irradiation causes these impurities to migrate towards individual grain boundaries at elevated temperatures In particular, helium (which is insoluble in metals) penetrates into grain boundaries in the form of bubbles and then weakens these grain boundaries. Therefore, the plasticity of the material after radiation decreases, which is the appearance and the formation of helium bubbles and other variants. It is caused by the decrease of the boundary strength due to the growth. The degree of embrittlement also becomes deeper due to the irradiation strengthening of the grains inside the above materials. When the grains become stronger, the strength of the grain boundaries between the grains decreases. All Everything shows that many cases are the cause of radiation embrittlement.

The combination of RDs with impurities, vacancies, their complexes, and defects that form local energy bands in the forbidden band have different thermal stabilities and have different effects on the properties of the crystal.

A series of physical effects related to the presence of high concentrations of RDs in sapphire can be extended. These effects include irradiation-induced diffusion, irradiation-induced phase transitions, blistering, and formation of defect superlattices. The response content of sapphire for these factors will allow for the development of sapphire resistance Enhanced and applied to more complex working conditions.

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