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The redistribution of carbon and manganese in weldments of manganese steels
Král, Lubomír ; Zlámal, B. ; Million, Bořivoj
In this paper, the results of diffusion C and Mn measurements in diffusion couples in steels with content of manganese in range 0-15 wt.% are discussed. The diffusion and thermodynamics characteristics were evaluated by using stationary model (SM). The ratio n does not agree with condition of quasistationary model (QSM) n=2 for solution of diffusion in these diffusion couples. In the paper, the results of carbon redistribution for n=2 a n= 2,8-3,7 for diffusion couples shown above are confronted each other. The part of this paper attend to more detailed description of structure changes on weldments interface in diffusion couples 0.28C-0.04Mn/0.31C- 5.01Mn a 0.28C-0.04Mn/0.34C-15.04Mn (wt.%).
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Strukturní změny ve slitinách Fe91-yMo8Cu1By – srovnání vlivu difuzivit Fe a Mo
Čermák, Jiří ; Stloukal, Ivo
Partly crystallized alloys Fe91-yMo8Cu1By belong to a NANOPERM-type family with excellent soft-magnetic behavior. Molybdenum, as an alloying element, causes that the Currie temperature of both amorphous and nano-crystallized form of the alloys is close to the room temperature, which opens possibilities to numerous applications. In the present work, structure changes of three chosen alloys (y = 12, 15, 17) are investigated after several temperature treatments by TEM, XRD and DSC and diffusivity of the principal metallic components is measured in the temperature interval 548 – 773 K. It was found that bulk diffusion coefficients of Fe and Mo in relaxed amorphous state are about the same, but grain boundary diffusivity of Fe is much higher than that of Mo. Such a difference in grain boundary diffusivity may act as structure stabilizing factor.
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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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Difúze 99Mo ve teplně zpracované slitině Fe76Mo8Cu1B15
Čermák, Jiří ; Stloukal, Ivo
Ion beam sputtering by Ar+ ions was used to investigate 99Mo tracer diffusion in Fe76Mo8Cu1B15 alloy in the temperature range 548 – 648 K. The experimental samples were prepared from ribbons of Fe76Mo8Cu1B15 alloy in as quenched state q, and after pre-annealing at 683 K for 1 h (state a1) and at 743 K for 1 h (state a2). The penetration profiles were obtained using serial sectioning method and consist of two parts suggesting that two different diffusion paths are operating. The Mo short-circuit diffusivity P was evaluated using both LeClaire’s analysis and Divinski’s theory derived for transition type-A/B regime in coarse-grained materials.
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