Selective laser melting of Zn–Ag alloys for bone repair: microstructure, mechanical properties and degradation behaviour

ABSTRACT

Zn possesses good biodegradability and biocompatibility, but its strength and hardness are insufficient for bone implants. In this study, Ag was introduced into Zn to improve the mechanical properties by selective laser melting. The results showed that Ag was dissolved in Zn, which generated constitutional undercooling in front of the advancing solid/liquid interface during solidification, making more nucleation events occur and thus refining the grains. When Ag content exceeded its solid solubility in Zn, AgZn₃ phase is formed, which acted as active nucleation sites for Zn grains, further refining the grains. The refinement of the grains effectively hindered the plastic deformation and dislocation. As a result, the compressive strength and hardness were improved by about 100% and 116%, respectively. When Ag content continued increasing and became excessive, AgZn₃ phase grew rapidly, coarsening the grains. Accordingly, the mechanical properties slightly decreased. These results demonstrated that the Zn–Ag alloys are potential implant biomaterials.

KEYWORDS:

• Zn–Ag alloys
• selective laser melting
• microstructure
• mechanical properties
• degradation behaviour

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

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

Notes on contributors

Cijun Shuai

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.

Lianfeng Xue

Mr. Lianfeng Xue is a postgraduate of Central South University.

Chengde Gao

Prof. Chengde Gao is a professor of Central South University. He works as a chief editor or editoral board member of many international journals, such as Journal of Engineering Mechanics and Machinery, and Journal of Osteoporosis and Physical Activity. He also works as invited reviewer for more than 20 international journals. He has published more than 60 SCI indexed papers and obtained 5 patent declarations and authorisations.

Youwen Yang

Dr. Youwen Yang is a doctor of Central South University. He has published more than 10 papers and obtained 5 patent declarations and authorisations.

Shuping Peng

Prof. Shuping Peng is a professor of Xiangya School of Medicine. 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.

Yanru Zhang

Miss. Yanru Zhang is a postgraduate of Central South University.