Mechanické vlastnosti a struktura mikrokrystalických materiálů

Abstract

Mechanical properties and structure of microcrystalline materials Krystof Turba Abstract In thepresent work, high temperature deformation of anAl - 4,5Mg~ 0,2Zr - 0,2 Sc alloy produced by equal-channel angular pressing (ECAP) was studied. The aim of the investigation was to find a correlation between the mechanical properties of the material at elevated temperatures and its specific microstructure resulting from the severe plastic deformation during ECAP. Special attention was devoted to the stabilizing effect of the Zr and Sc additions on the ultra-fine grained (UFG) microstructure at elevated temperatures and its possible consequences for the occurrence of superplastic behavior. The material with 6 passes of ECAP at 523 K, route BC, was studied using the methods of light microscopy (LM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). A series of tensile tests were performed at temperatures between 573 and 823 K. The grain size after ECAP was found to be < 1 jim and remained < 10 fxm up to a temperature as high as 798 K. This outstanding stability of the UFG microstructure can be attributed to the presence of Al3(ZrxSci_x) precipitates. Consequently, the studied alloy exhibited high strain rate superplasticity over a broad interval of temperatures ranging from 573 to 798 K....

Mechanicke vlastnosti a struktura mikrokrystalickych materialu Krystof Turba Abstrakt Prace se zabyva vysokoteplotni defonnaci slitiny Al -4,5 Mg - 0,2 Zr -0,2 Sc pripravene raetodou uhloveho protlacovani s konstantnim prufezeni (ECAP). Jejim cilem bylo nalezt korelaci mezi mechanickymi vlastnostmi studovaneho materialu za zvysenych teplot a jeho specifickou mikrostrukturou, vytvofenou v dusledku intenzivnl plasticke deformace behem protlacovani. Zvlastm pozornost byla venovana vlivu prirnesi Zr a Sc na teplotni stabilitu ultrajemnozrnne mikrostruktury a jeho dusledkum pro vznik superplastickeho chovani. Material s sesti pruchody ECAP cestou BQ pri teplote 523 K byl studovan rnetodarni svetelne mikroskopie (LM), transmisni elektronove tnikroskopie (TEM) a mikroskopie atomovych sil (APM). V teplotnim intervalu rnezi 573 a 823 Kbyla provedena serie deformacnich zkousek vjednoosem tahu. Mikrostruktura studovane slitiny po ECAP byla ultrajemnozrnna, s prumernou velikosti zma < 1 p.m. Velikost zrna navic ziastala pod hranici 10 jam az do teploty 798 K. Tato rnimofadna stabilita ultrajenmozrnne mikrostruktury, ktera je dusledkem pntomnosti precipitatu Al3(ZrxSci_x), umoznila superplasticke chovani materialu vsirokem oboru deformacnich teplot. Material vykazoval vysokorychlostni superplasticitu pfi teplotach 573...