Effect of Sc addition on low-cycle fatigue properties of extruded Al-Zn-Mg-Cu-Zr alloy

ABSTRACT

The influence of minor Sc addition on the low-cycle fatigue (LCF) properties of hot-extruded Al-Zn-Mg-Cu-Zr alloy with T6 state was investigated through performing the LCF tests at room temperature and air environment. The results indicate that two alloys show cyclic stabilisation, cyclic hardening and cyclic softening during fatigue deformation. The addition of Sc can significantly enhance the cyclic stress amplitude of the alloy. Al-Zn-Mg-Cu-Zr-Sc alloy shows higher fatigue lives at lower strain amplitudes, while has lower fatigue lives at higher strain amplitudes. For the two alloys, the density and movability of dislocations are related to the change of cyclic stress amplitudes. The existence of Al₃(Sc,Zr) phase can inhibit the appearance of cyclic softening phenomenon in the Al-Zn-Mg-Cu-Zr-Sc alloy.

KEYWORDS:

• Al-Zn-Mg-Cu-Zr alloy
• element scandium
• low-cycle fatigue
• fatigue fracture
• microstructure

Acknowledgements

The authors would like to thank Dr S.Q. Zhang for her experimental supports and fruitful discussion.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Qingyan Zhu http://orcid.org/0000-0002-7056-3568

Additional information

Funding

The financial supports provided by Key International S & T Cooperation Project of P. R. China and Foundation of State Key Laboratory of Rolling and Automation, Northeastern University (2018RALKFKT010) are greatly appreciated.