J. Mater. Sci. Technol. ›› 2020, Vol. 46: 44-49.DOI: 10.1016/j.jmst.2019.11.032

• Research Article • Previous Articles     Next Articles

Interactions between cadmium and multiple precipitates in an Al-Li-Cu alloy: Improving aging kinetics and precipitation hardening

Liang Wua,b, Yugang Lib, Xianfeng Lia,*(), Naiheng Maa,b, Haowei Wanga,b   

  1. aState Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China
    bSchool of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China
  • Received:2019-08-06 Revised:2019-10-11 Accepted:2019-11-10 Published:2020-06-01 Online:2020-06-19
  • Contact: Xianfeng Li


This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd (0.06 at.%). The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations. A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner. Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets. It is highly likely that these nanoparticles act as heterogeneous nucleation sites, which consequently leads to a higher number density of T1 precipitates. Moreover, Cd atoms were preferentially segregated within δ′ precipitates, which can be attributed to the strong bonding between Li and Cd. The interactions between Cd and the T1 (Al2CuLi) and δ′ (Al3Li) precipitates in Al-Li-Cu alloy are first reported. The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.

Key words: Aluminum alloys, Three-dimensional atom probe (3DAP), High-angle annular dark-field (HAADF), Precipitation, Cadmium