Quantitative Microstructure and Defect Density Analysis of Polycrystalline Tungsten Reference Samples after Different Heat Treatments

Abstract

In order to provide a solid basis for the correlation of microstructure and hydrogen isotope retention in tungsten, reference samples with different microstructures were prepared from a single batch of polycrystalline tungsten by standardised polishing and heat treatment procedures. Representative samples were analysed by scanning electron microscopy and scanning transmission electron microscopy as well as by electron backscatter diffraction. We show that if the annealing temperature is increased from 1200 to 1500 K, practically only the density of dislocations and grain boundaries with very small misorientations of less than 2° is reduced, while for annealing at 1700 and 2000 K, also the density of high-angle grain boundaries is reduced due to grain growth. Furthermore, the dislocation density is reduced by nearly two orders of magnitude compared to tungsten annealed at 1200 K. We also comment on two different textures on the front and rear side of the samples that were observed both by X-ray diffraction and EBSD.

Deuterium retention and morphological modifications of the surface in five grades of tungsten after deuterium plasma exposure

“…For the rolled tungsten from Plansee (WP-R) the (sub-)grain dimension perpendicular to the plate surface is the smallest with 0.5-1 µm, while parallel to the surface the typical size is 1-5 µm [26,27] (see section 2.4). For this specimen type, the plate surface is the surface exposed to the plasma.…”

“…The two faces of the specimens of the rolled Plansee material have different rolling texture, one dominated by (100) and (111) planes parallel to the surface and the other by (110) planes, i.e., still easily recognisable after recrystallization [27]. These textures are slightly altered by the recrystallization procedure [27]. For the specimen rc-WP-R the side dominated by (110) planes was exposed to the plasma, while for the specimen WP-R the side dominated by (100) planes.…”

“…That means the sub-grains separated by small-angle boundaries are detected and their size and shape is determined [27] (section 2.1).…”

Hydrogen isotope accumulation in the helium implantation zone in tungsten

“…Sample size was 12×15 mm 2 , thickness 0.8 mm. It was chemo-mechanically polished to a mirror-like finish [ 14 ] and then heated for 2 min in ultra-high vacuum at 2000 K for recrystallization. This procedure enlarges the grain size to 10 -50 μm with (100) being the preferential grain orientation [14].…”

“…It was chemo-mechanically polished to a mirror-like finish [ 14 ] and then heated for 2 min in ultra-high vacuum at 2000 K for recrystallization. This procedure enlarges the grain size to 10 -50 μm with (100) being the preferential grain orientation [14]. As all the annealing experiments presented here were conducted in-situ we could use one single sample thereby avoiding any influence of sample preparation.…”