Mechanical properties and structure of microcrystalline materials

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...