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Enhanced nucleation and precipitation hardening in Al-Mg-Si(-Cu) alloys with minor Cd additions

Abstract

This work reports a novel effect of impurity element Cd on enhancing the precipitation kinetics and increasing the peak hardness of Al–Mg–Si(–Cu) alloys during artificial ageing. It is found that the number density of age hardening Mg–Si(–Cu) precipitates is greatly increased by Cd addition (~0.06 at.%) at both the under-aged and peak-aged stages. A systematic study on the precipitation behaviour by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) shows that most Mg–Si(–Cu) precipitates in the Cd-containing Al–Mg–Si alloys are associated with Cd-rich precipitates and have highly disordered structures. It is also found that the formation of Q'/C-like sub-units in Mg–Si(–Cu) precipitates is significantly promoted by Cd additions. To explore the nucleation mechanism under the influence of Cd addition, atom probe tomography (APT) is applied to study the solute clustering behaviour in the early stages of artificial ageing, and density functional theory (DFT) calculations are used to evaluate the binding energies of different solute-vacancy complexes and therefore the formation kinetics of Mg–Si–Cd clusters.
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Category

Academic article

Language

English

Author(s)

  • Feng Qian
  • Dongdong Zhao
  • Eva Anne Mørtsell
  • Shenbao Jin
  • Junsheng Wang
  • Calin Daniel Marioara
  • Sigmund Jarle Andersen
  • Gang Sha
  • Yanjun Li

Affiliation

  • SINTEF Industry / Materials and Nanotechnology
  • Norwegian University of Science and Technology
  • Beijing Institute of Technology
  • Nanjing University of Science and Technology

Year

2020

Published in

Materials Science & Engineering: A

ISSN

0921-5093

Volume

792

View this publication at Norwegian Research Information Repository