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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.
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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.
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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.
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Simulated element redistributions in Ni-based superalloys weldments
Brož, P. ; Buršík, Jiří ; Sopoušek, J. ; Picha, R.
The diffusion and phase precipitation processes in welded joints of pure Al-Cr-Ni system and low alloyed Al-Cr-Ni-X systems (where X means Co, W, or Ti) were simulated using CALPHAD method and DICTRA software. The equilibrium calculations allowed to predict phase diagram cross-sections for the Al-Cr-Ni-X systems. The performed simulations based on local equilibrium condition in diffusion couple enabled to describe the phase transformation process and obtain redistribution of alloying species, activity profiles, and other time-distance dependences for other relevant values in diffusion-affected zone of the Al-Cr-Ni / Al-Cr-Ni-X weldments.
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Diffusion of galium in polycrystalline Ni3Ga
Mareček, P. ; Fous, T. ; Čermák, Jiří
The diffusion of 67Ga radiotracer in polycrystals of Ni3Ga intermetallic was studied by residual activity method. Both volume- and grain boundary diffusivity was investigated and quantitatively described. Obtained diffusivites of Ga in Ni3Ga lattice show the increasing dependence on increasing Ga concentration.
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Diffusion in Ni3Al-Co intermetallic
Gazda, A. ; Čermák, Jiří
Interdiffusion in Ni3Al intermetallic alloyed by 0-19 at %Co was studied in the temperature range 900-1200 C. An attempt was made, to analyze the interdiffusion coefficient into intrinsic diffusivities of individual components.Since no detecatble shift of inert markers was observed, it was concluded that the intrinsic diffusivities of Ni,Al and Co are aproximately equivalent one to another. The interdiffusion in pseudobinary alloys Al/Ni runs slightly faster than that in pseudobinary alloys Ni/Co. Measurements of 63Ni radiotracer in Ni3Al-Co was measured at 1000-1200 C by residual activity method. Enhanced Ni volume diffusivites observed at 1200C are most likely due to short-circuit diffusion along interphase boundaries in beta + gamma with comma field. The grain boundary diffusion of 63Ni was estimated at 1000C and 1100C. It was in a good agreement with our previous measurements made with pure Ni3Al.
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