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Influence of Microstructure Changes on the Mechanical Behaviour of Aluminium Processed by ECAP Method
Král, Petr ; Dvořák, Jiří ; Svoboda, Milan ; Sklenička, Václav
Extremely coarse – grained aluminium (99.99 %) was subjected to severe plastic deformation (Equal-Channel Angular Pressing) at room temperature. The properties of the ECAP material may considerably differ from properties of material with a standard coarse grain size. The largest changes of microstructure take place during the first four ECAP passes. Thus, the microstructure after twelve passes consists of roughly equiaxed grains (~m) with high fraction of high angle boundaries (~70%). In this work the behaviour of ECAP material with different number of passes at the tensile and creep tests has been studied. It is shown that ECAP aluminum provides a significant increase of the ultimate strength, however, there is low strain hardening during tensile deformation. The creep resistance of aluminum increased considerably already after one ECAP pass. However, repetitive ECAP pressing lead to a noticeable degrease in the creep properties. ECAP microstructure was examined in terms of the inhomogeneity. The results indicate that an inhomogeneity of the ECAP microstructure may influence the creep behaviour of the ECAP material.
MICROSTRUCTURE/PROPERTIES RELATIONSHIP IN ULTRAFINE GRAINED ALUMINIUM PROCESSED BY ECAP TACHNIQUE
Král, Petr ; Dvořák, Jiří ; Svoboda, Milan ; Sklenička, Václav
Experiments were conducted on pure ultrafine grained aluminium processed by severe plastic deformation using the equal ů channel angular pressing ů ECAP technique. By this technique bulk ultrafine grained material was prepared. The propertis of this material considerably differs from properties of material with standard grain size. It was found that microstructure of ultrafine grained aluminium after one pass by the ECAP die contains subgrains and these subgrains are changed by subsequent ECAP passes in grains separated by high angle grain boundaries. In this work special attention is given to the stability of microstructure and the relationship between microstructure and mechanical properties of ECAP material.
MECHANISMY CREEPOVÉ DEFORMACE U UTRAJEMNOZRNNÉHO HLINÍKU PŘIPRAVENÉHO METODOU ECAP
Dvořák, Jiří ; Sklenička, Václav ; Král, Petr
Extremely coarse-grained aluminium (99,99%) was subjected to severe plastic deformation (ECAP)for obtain an ultrafine-grained microstructure. Creep tensile and compression tests were conducted on such material and for comparison reasons also on coarse-grained aluminium. The results indicate an increased creep resistant of ultrafine-grained aluminium compared to its coarse-grained state. It was proposed, that creep of ultrafine-grained aluminium is probably control by the same creep mechanisms as coarse-grained one. However, the role of grain boundary sliding in creep considerably differs in both ECAP and coarse-grained materials

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