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Creep behaviour of Al-0.2%Sc alloy processed by ECAP Method
Dvořák, Jiří ; Král, Petr ; Kvapilová, Marie ; Sklenička, Václav
An Al-0.2wt.%Sc aluminium alloy was subjected to equal-channel angular pressing (ECAP) at room temperature to refine its coarse – grain size corresponding to its as-received state. For this purpose the ECAP die was used which had a 90° angle between the die channels. By application of this method at room temperature an ultrafine-grained microstructure was achieved with the grain size of ~ 0.3mm after 8 ECAP passes by route BC. Following creep tests in tension were performed at 473 K and at applied stresses ranging from 10 to 50 MPa on ECAP material and, for comparison purposes, on unpressed one. The results indicate, that the creep resistance of ECAP material is markedly lower after 8 passes in comparison with creep behaviour of coarse – grained one. The detrimental effect of ECAP on the creep resistance is probably caused by increasing contribution of grain boundary sliding to the overall creep deformation.
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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.
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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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