Recent Progress in Understanding the Durability and Damage Tolerance of AIRWARE Products

In addition to the well-known benefits of Li addition for density and Young’s modulus, modern Al-Cu-Li alloys such as Constellium’s AIRWARE products show improved fatigue performance, corrosion resistance, and damage tolerance compared with equivalent strength Li-free products. These improved property balances have resulted in the recent commercial success of these alloys.  However, the underlying metallurgical mechanisms are generally less well understood than in conventional alloys.

 Over the last decade, Constellium has instigated many fundamental studies of the corresponding microstructure-property relationships. In this paper, the results of such studies will be reviewed in the context of achieving the key properties for aerospace products.  For example, achieving appropriate levels of strength-toughness balance in these alloys requires mastery of the T1 nucleation kinetics, achieved by micro-alloying approaches.   Improvements in fatigue performance are linked to the nature and distribution of intermetallic particles as well as the underlying crack growth behavior.  The improved corrosion resistance can be linked both to the near-grain boundary copper concentration profile and to the influence of the T1 precipitates.  Damage tolerance improvements depend both on strain mechanisms and on the specific grain structures and textures observed in these alloys.

Throughout the presentation, outstanding knowledge gaps will be highlighted as well as potential approaches to addressing them.