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Mechanismus difúze 88Y ve slitině QE22
Čermák, Jiří ; Stloukal, Ivo
Diffusion of radioisotope 88Y was studied in magnesium-based alloy QE22 (nominal composition: Mg – 2 RE – 2.5 Ag – 0.6 Zr in wt. %, RE – rare earth metal) in temperature interval ranging from 648 K to 728 K. Diffusion behavior of the chosen tracer, which is suitable for diffusion measurements, simulates the typical migration characteristics of mischmetal components in general. Mixture of RE’s used for alloying contains Ce and Nd as principal elements and it is added in QE22 to promote the creep resistance. It was found that yttrium diffuses along dislocations that act as paths of rapid diffusion. Diffusivity of 88Y along dislocations, a2sDd, was estimated.
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Heterodifúze 65Zn v binárních slitinách Mg - x Al av komerční slitině AZ91
Čermák, Jiří ; Stloukal, Ivo
Bulk diffusion coefficient of Zn, D, in Mg – x Al model alloys (x = 0, 1.8, 3.9 and 9 at. %), in commercial alloy AZ91 and in intermetallic compound Mg17Al12 intermetallic was measured by residual activity and serial sectioning methods. Composition dependence of D was obtained, that shows a slight increase of D with increasing Al concentration. Measurements were done at several diffusion temperatures, which enabled to evaluate the pre-exponential factor and the activation enthalpy of Zn diffusion.
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Difúze 65Zn ve dvoufázové eutektické slitině Mg - 33 wt.% Al
Čermák, Jiří ; Stloukal, Ivo
Diffusion of zinc in a two-phase eutectic alloy Mg – 33 wt.% Al and in its components, Mg – Al solid solution and in the intermetallic compound Mg17Al12, was studied. The measurement of Zn diffusion coefficient was carried out by radiotracer technique in temperature interval 498 – 848 K. Zinc is believed to simulate the migration behavior of magnesium. It was observed that the interphase boundaries do not act as short-circuit paths. The study of the stability of the eutectic structure enabled to estimate the mean specific energy of the (Mg)/ Mg17A12 phase interface.
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