Anisotropy of Self-Diffusion in Alpha Uranium

Abstract

Self-diffusion along the three principal crystallographic directions of alpha uranium has been measured on mosaic structured single crystals by the tracer-sectioning method. The diffusion coefficients at 625.5°C are D[100]=D[001]=1.95×10−13 cm2/sec,D[010]⩽10−14 cm2/sec. It appears that the mosaic structure has not affected the diffusion significantly.

On the accurate description of uranium metallic phases: a MEAM interatomic potential approach

“…However, it should be kept in mind that their study only considers the atomic jump through interstitial holes in αU and does not take into account dumbbell configurations, which are more anisotropic. In tracer diffusion experiments on αU, it is observed that D xx ∼ D zz D yy [71] in agreement with the present results for the vacancy mechanism. Neutron irradiation experiments also show a large growth anisotropy in which a crystal of αU increases its length in the [0 1 0] direction and decreases in the [1 0 0] direction, while in the transverse [0 0 1] direction no dimensional changes are observed [72].…”

Calculation of Vacancy Properties in Pure U

“…Los resultados de DM muestran que la difusión es más rápida en la dirección [100] que en las [010] y [001], mientras que los resultados de MC indican que también existe difusión rápida en la dirección [001]. Se observa que los resultados del cálculo estan en buen acuerdo con la idea original de Seigle y Opinsky y algunos datos experimentales (7,8) . Tanto las curvas de la Fig.…”

“…Resnick y Seigle (6) no hallaron una gran anisotropía en la difusión a 640C medida en monocristales, aunque reconocieron que la técnica radiográfica utilizada poseía poca precisión. Por otro lado, Rothman y col. (7,8) encontraron que Uγ de altas temperaturas (1048K<T<1405K), se conoce que ésta es anómala pues resulta muy alta, igualmente a lo observado en las fases bcc de Ti, Zr y Hf (1) .…”

Thermomechanical Response of Polycrystalline alpha-Uranium

“…Such discrepancy between the single crystal experiments and polycrystal models, with regards to the CRSS ratios between hard and soft slip modes has been noted previously [36,37]. Because the tests were conducted at relatively high homologous temperature ( [34], but in the current temperature range di↵usion is most likely along high di↵usivity paths such as dislocation cores and grain boundaries, which would not readily explain the anisotropy in the relaxation mechanism.…”