The interaction of proton irradiation with Zr textured microstructure

Proton irradiation is commonly used as a surrogate for neutrons in experimental studies of structural materials for thermal reactors, such as Zr alloys. The proton beam is unidirectional which requires a choice to be made about the direction of the beam relative to the sample. The direction of the proton beam will determine what lattice orientations the protons will predominantly interact with, particularly in a sample with a strong texture. Since protons can be channelled the orientation of the crystal will affect the energy deposition and the implantation range. We have therefore investigated the degree of high energy proton channelling in crystal orientations found in a strongly textured sample of Zr. We find that the crystal orientations near low-index crystal directions like the 〈112¯0〉 zone axis encourage a higher degree of proton channelling compared with other crystal orientations commonly found in a split-basal textured sample. Channelling in these orientations can change the energy deposition of protons by 40%. Our results show that care must be taken when quantifying the damage in textured samples using a single grain orientation. To compensate for channelling effects, the damage from ion irradiation in a textured sample should be quantified by averaging the damage across many different grain orientations, especially when the irradiation temperature of the bulk is less than 300 K.