Microstructural characterization & viscoelastic properties of AlZnMgCu alloys for aerospace applications

Abstract

The mechanical properties of materials (and particularly the viscoelastic properties) are intimately linked to their microstructure. Thereby, microstructural transformations are reflected on the viscoelastic behaviour. Fatigue, for instance, is a consequence of microstructural changes induced by the viscoelastic response of a material under repeated loading. Accordingly, the characterization of the viscoelastic response of a material offers an alternative method for analyzing the microstructure, phase transformations (e.g. nucleation and growth, precipitate redissolution) and fatigue behaviour, aside from enabling a deeper understanding of other technologically essential properties, like damping, yielding, etc.

In the present work, the viscoelastic behaviour of commercial AlZnMgCu alloys is studied by means of dynamic-mechanical analysis, and the results are combined with calorimetric data and optical and electron microscopy data. These alloys are suitable to a number of industrial applications, and are of particular importance in the aerospace sector and transport industry.

This research is aimed at the identification and characterization of the effects of temperature, frequency of dynamic loading, microstructure and phase transformations on the viscoelastic behaviour of the mentioned alloys and the mechanical relaxation processes taking place. Ultimately, this research pursues to characterize the relation between the viscoelastic response of AlZnMgCu alloys under given operational conditions and their fatigue behaviour.