Comparative Analysis of Experimental Techniques for Microstructural Engineering of Novel Nanostructured Aluminium Alloys

Abstract

Precipitation holds a pivotal role in comprehending the intrinsic behavior of materials. In the design of nanostructured metallic alloys, precipitates have recently been studied to increase the alloys’ stability and response under extreme environmental conditions. Studies on precipitation often rely on conventional and ex situ electron-microscopy methods, but a systematic investigation that compares different techniques and its microstructural implications are rarely available. In this context, we employed a novel ultrafine-grained AlMgZnCuAg crossover alloy to compare three distinct methodologies for investigating the precipitation sequence: (i) ex situ transmission electron microscopy (TEM) from bulk heating, (ii) ex situ TEM from TEM foil heating, and (iii) in situ TEM with microelectromechanical-system (MEMS) heating. Although the heat treatment procedure was consistent across all cases studied, the application of these three different experimental techniques in the same alloy system resulted in significantand non-negligible differences in the final precipitation behaviour. Ultimately, it resulted in observable microstructural variations and precipitates with distinctively different shape and sizes and, as a result, we outline herein the major similarities and differences among these techniques to achieve comparable results. This knowledge will help to compare and assess results of precipitation sequences obtained with different techniques.

Keywords: Precipitation analysis, (in situ) Transmission Electron Microscopy, Aluminium crossover alloy, STEM-EDX analysis, heat treatment