Abstract
Self-diffusion coefficients ( D) have been measured in nominally pure (NP) α-Zr single crystals (= 50 ppm Fe) in the range 867–1107 K, in directions either parallel (Dpa) or perpendicular ( D pe) to the c-axis. Measurements were also made on high-purity (HP) α-Zr single crystals (< 1.0 ppm Fe) at 1110 K. The diffusion profiles were determined by sectioning and radio-tracer ( 95 Zr) counting. Sectioning was done with a sputtering device, or a microtome (some NP experiments at 1107 K). D values for NP Zr are about an order of magnitude higher than the corresponding values for HP Zr. Diffusion anisotropy is complicated. The sputter-sectioned NP Zr specimens show increasing anisotropy ratios (AR = Dpa/Dpe), from 1.0 to 3.2, with decreasing temperatures, whereas AR = 0.53 for both the microtome-sectioned NP and sputter-sectioned HP Zr: the low AR value is consistent with expectations based on intrinsic self-diffusion in hcp metals with c/a < 1.633.
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