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Difúze C a Mn ve svarovém spoji Fe-0,3C/Fe-0,3C-15Mn
Král, L. ; Million, Bořivoj ; Čermák, Jiří
Příspěvek obsahuje výsledky měření difúze C a Mn ve svarových spojích ternárních slitin Fe-0,3C/Fe-0,3C-15Mn. Slitiny byly odlity v laboratorní indukční peci v ochranné atmosféře Ar. Ingoty byly vykovány do tvaru tyčí kruhového průřezu o průměru cca 15mm a homogenizačně žíhány. Po tepelném zpracování byly obrobeny na průměr 12mm a rozřezány na tloušťku 4mm. Vzorky byly metalograficky broušeny a svařeny elektrickým šokem. Difúzní páry byly ve vakuu zataveny do křemenných ampulí společně s titanovými třískami. Byly žíhány při teplotách 1100-800°C po dobu 1,5-96h. Měření redistribuce uhlíku a manganu bylo provedeno pomocí úsečkové vlnově disperzní mikroanalýzy na rastrovacím mikroskopu Philips SEM-505 s analyzátorem Microspec WDX-2A ve směru kolmém na svarové rozhraní. Byly stanoveny difúzní koeficienty uhlíku a manganu a objasněny vztahy mezi nimi.
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A new method of estimation of diffusion characteristics in ternary systems
Čermák, Jiří ; Rothová, Věra ; Gazda, Aleš
A method was proposed based on an estimation of components of diffusion matrix, Dij, in ternary systems. It makes possible to obtain the concentration dependence of DijŽs in a wide range of concentrations using one diffusion couple only. It is in contrast to the conventional procedure that needs two diffusion couples and provides DijŽs for a single composition related to an intersection of diffusion paths. The method was applied to gammaŽ one-phase interdiffusion in Ni3Al-X (X = Cr, Fe, Nb, Ti) in temperature interval 1173 ů 1533 K.
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In-situ monitoring of phase transformation in Ni3Al based alloys by means of hydrogen permeation measurement
Rothová, Věra ; Čermák, Jiří
Nickel aluminide Ni3Al crystallizes in the cubic L12 structure (Cu3Au type). It is known from the literature that this structure remains unchanged up to the melting point. However, under certain circumstances, it can change from L12 to other non-cubic ordered crystal structures. There have been reported some data which indicate that the presence of hydrogen may facilitate the change in the structure. Present detailed study of hydrogen permeation behavior in both the Ni3Al and the CMSX-4 has shown very sensitive changes of permeation rate depending upon temperature variations.
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Diffusion of Ni and Ga along High-Diffusivity Paths in polycrystalline Ni3Ga
Čermák, Jiří ; Rothová, Věra
The volume and grain boundary (GB) diffusion of 63Ni and 67Ga radiotracers in polycrystals of Ni3Ga intermetallic was studied in the vicinity of stoichiometric composition A3B (23.5 - 28.3 at. % Ga). Both volume- and GB diffusivity was measured in the temperature interval 773 - 1373 K by residual activity method. Obtained Ga volume diffusivity increases with increasing Ga concentration x(Ga); the increasing tendency of Ni volume diffusivity with increasing x(Ga) is pronounced especially at lower temperatures. GB diffusivity of both Ga and Ni in Ni3Ga are close one to another and contrary to diffusion behavior of components in Ni3Al - they do not show any significant dependence on x(Ga).
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