|
| |
|
|
Vzájemná difúze v systému Mg/Mg17Al12
Rothová, Věra ; Čermák, Jiří
Light Mg-based alloys are perspective materials for automotive industry. The presence of the brittle phase Mg17Al12 in the structure of the materials causes, however, certain problems in their production and during the application. It is known that desirable mechanic parameters can be easily achieved by a special annealing which leads to a less-harmful morphology of Mg17Al12 phase. The physical background of the process consists in the diffusion-controlled redistribution of components in the alloy. In the present work, the interdiffusion coefficients were measured in diffusion couples made of Mg and Mg17Al12. The results may contribute to an optimization of production process.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
| |
|
|
Difúzní studie Fe a Mo ve slitině Fe76Mo8B15Cu1
Čermák, Jiří ; Stloukal, Ivo
59Fe and 99Mo tracer diffusion in Fe76Mo8B15Cu1 alloy was studied using serial sectioning method in the temperature range 527 – 649 K. The ribbon-like samples were annealed at 695 K for 1 and 5 hours before the diffusion experiments; the volume fraction of crystalline phase was checked by the Mössbauer spectroscopy. Concentration profiles obtained by sputtering by Ar+ ions in a glow discharge show two distinct branches suggesting that two diffusion paths are operating.
|
|
| |
|
|
Přístroj pro měření koncentračních profilů – Analýza výstupních dat
Čermák, Jiří ; Stloukal, Ivo
In this paper, a new modification of a commercial apparatus Edwards Coating system E306A is described that enables to perform diffusion measurements with radioactive tracers. The plan-parallel thin layers are removed by sputtering with Ar+ ions and the well defined fraction of the sputtered-off material is sequentially collected. The function of the apparatus is exemplified by the measurement of bulk diffusion coefficient of 65Zn in Fe40Ni40B20 alloy at T = 684 K.
|
|
|
Difúze 71Ge a 68Ge v Mg a ve slitině Mg-2Al
Čermák, Jiří ; Eversheim, D. ; Rothová, Věra ; Stloukal, Ivo
Measurement of Ge diffusion coefficients in Mg and in Mg-1.8 wt.% Al alloy is presented in this work. Two techniques of Ge deposition and two annealing atmospheres (Ar and Ar + Cl2) were tested which might reveal possible influence of hold-up effect at the free surface on the diffusion behavior. The present results are compared with the literature data for volume diffusion of other impurities in Mg.
|
guest ::
