Wrapping effect of secondary phases on the grains: increased corrosion resistance of Mg–Al alloys

ABSTRACT

The discrete secondary phases usually cause severe galvanic corrosion, thereby resulting in rapid degradation for Mg–Al alloys in orthopaedics application. In this study, CaO was introduced into Mg–Al–Zn (AZ61) alloy via selective laser melting (SLM) to ameliorate the characterisations of the secondary phases, with an aim to improve its corrosion behaviour. Results revealed that CaO reacted with Mg and Al in Mg–Al alloys during SLM, suppressing the formation of coarse Mg₁₇Al₁₂ phase and promoting the formation of (Mg, Al)₂Ca phase. Meanwhile, the rapid solidification during SLM promoted the homogeneous precipitation of the second phase. As a result, inert (Mg, Al)₂Ca phase homogeneously wrapped the Mg grains, which effectively protected them from the invasion of corrosion solution. Thus, the degradation rate was remarkably reduced from 0.073 to 0.031 mg cm^–2 h^–1. Furthermore, AZ61-9CaO exhibited good cytocompatibility. This work suggested that AZ61-9CaO was promising candidates for orthopaedics implants.

KEYWORDS:

• Mg–Al alloys
• corrosion resistance
• continuous secondary phases
• wrapping effects

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Prof. Cijun Shuai is a professor of Central South University. He works as a chief editor or editorial board member of many international journals, such as Current Biomedical Engineering, BioMed Research International, etc. He also works as invited reviewer for more than 30 international journals. He has published more than 180 papers and obtained 44 patent declarations and authorisations.

Mr. Chongxian He is a postgraduate in Central South University. He has published 2 papers that are indexed by SCI.

Dr. Liang Xu is associate professor of School of Energy and Mechanical Engineering, Jiangxi University. He has published 8 papers that are indexed by SCI.

Dr. Quan Li is associate professor of School of Energy and Mechanical Engineering, Jiangxi University. He has published 9 papers that are indexed by SCI.

Dr. Tong Chen is associate professor of School of Energy and Mechanical Engineering, Jiangxi University. She has published 7 papers that are indexed by SCI.

Dr. Youwen Yang is a doctor of Central South University. He has published more that 12 papers that are indexed by SCI.

Prof. Shuping Peng a professor of Xiangya Hospital, Central South University. She works as chief editor or editorial board member of many international journals, such as BioMed Research International, International Review of Molecular Sciences and Mol Cancer, etc. She has published more than 60 SCI indexed papers.

Additional information

Funding

This work was supported by The Natural Science Foundation of China [grant number 51575537, 51705540, 81572577]; The Project of Innovation-driven Plan of Central South University [grant number 2016CX023]; Hunan Provincial Natural Science Foundation of China [grant number 2016JJ1027]; National Postdoctoral Program for Innovative Talents [grant number BX201700291]; The Open-End Fund for the Valuable and Precision Instruments of Central South University; The Project of State Key Laboratory of High Performance Complex Manufacturing, Central South University [grant number 2018zzts463]; and The fund of the State Key Laboratory of Solidification Processing in NWPU [grant number SKLSP201605].