Microstructural response to compression deformation of ultrafine-grained aluminum with various microstructures

Abstract

Ultrafine-grained aluminum having a variety of microstructural features such as fibrous grain morphology, strong or random texture and a dominance of low- or high-angle grain boundaries was compressed to 4% of true strain. This made it possible to measure yield strength and begin a microstructure evolution to accommodate an external load. The level of deformation was high enough to provide changes in the microstructure, but relatively low in order to make it possible to determine the deformation mode in grain types recognized in the pre-compressed condition, before they become unrecognizable. As a next step, a detailed EBSD examination of these samples before and after compression was performed to track those changes. These observations revealed that, in the samples with a fibrous microstructure, the role of particular fibers changes when the grain refinement is more pronounced within them. In the sample with a relatively uniform microstructure and a grain size of below 800 nm, the post-deformation observations indicated there had been significant grain rotations with a blurring of the initial texture. Based on our observations, we can state that the heterogeneity of plastic deformation mechanisms in ultrafine-grained aluminum is dependent on local variations in microstructure – the arrangement of defects and the crystallographic orientation.