Precipitation processes and structural evolutions of various GPB zones and two types of S phases in a cold-rolled Al-Mg-Cu alloy

Materials & Design

Calin D. Marioara¹  Xuanliang Chen²  Randi Holmestad³  Equo Kobayashi³  Jesper Friis⁴  Adrian Lervik⁴  Sigmund J. Andersen⁴ 

[1] Corresponding author.;Department of Materials Science and Engineering, Tokyo Institute of Technology, 2-12-1-S8-18, Ookayama, Meguro-ku, Tokyo 152-8552, Japan;Department of Physics, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, N-7491 Trondheim, Norway;Materials and Nanotechnology, SINTEF Industry, Høgskoleringen 5, N-7465, Trondheim, Norway;

关键词: Al alloy;    Precipitation;    Phase transformations;    Transmission electron microscopy;    Density functional theory calculation;   

DOI  :  

来源: DOAJ

【 摘 要 】

The Guinier–Preston–Bagaryatsky (GPB) zone and the S phase are the key strengthening precipitates in Al-Cu-Mg alloys. However, how their respective structures evolve during aging has not been fully understood. In this work, the age-hardening behavior and the precipitates in an Al–3Mg–1Cu (wt.%) alloy were investigated by means of Vickers hardness measurements, differential scanning calorimetry, transmission electron microscopy, and density functional theory calculations. A series of common GPB zones and a novel type of GPB zone named “GPBX” were observed in the cold-worked samples aged at 443 K for 20 min. In the subsequent aging, two types of S phases were found to coexist, labeled S-I and S-II phases. Density functional theory calculation results indicate that GPBX zone is stable and the S-I and S-II phases have almost the same formation enthalpy. Common GPB zones transform to S-I phases, while S-II phases are formed from GPBX zones preferentially along dislocation lines. The misorientation angles and morphologies of the S phases are also discussed. GPB zones were confirmed to be structurally linked to β” and U2 precipitates reported in 6xxx (Al-Mg-Si) series Al alloys. The revealed precipitate structures and their interrelationships may provide insights into future alloy design.

【 授权许可】

Unknown