Natural aging on Al-Cu-Mg structural hardening alloys - Investigation of two historical duralumins for aeronautics

This article presents the metallurgic study of sixty years old structural hardening Al-Cu-Mg alloys recovered from a double-deck aircraft Breguet 765. This study aims to characterize and understand the evolution of alloys over very long periods thanks to an approach coupling materials characterization and archives researches. The focus is made on two ancient age hardening Al-Cu alloys: A-U4G and A-U4G1, whose compositions are close to the international designations 2017A and 2024 respectively. Multi-scale structural investigation was carry out and mechanical properties were extracted. It is shown that despite natural aging during long periods, these alloys exhibit mechanical properties (yield strength, ultimate tensile strength and rupture strain) close to the expected original specifications.