Effect of Hydroxyapatite on the Mechanical Properties and Corrosion Behavior of Mg-Zn-Y Alloy

Chun Chiu,Chih-Te Lu,Keng-Liang Ou,Shih-Hsun Chen

doi:10.3390/ma10080855

Chun Chiu, Chih-Te Lu + Show 2 more

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https://doi.org/10.3390/ma10080855

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Journal: Materials	Publication Date: Jul 26, 2017
Citations: 18	License type: CC BY 4.0

Affiliation: National Taiwan University of Science and Technology

Abstract

Mg-Zn-Y alloys with a long period stacking ordered (LPSO) phase are potential candidates for biodegradable implants; however, an unfavorable degradation rate has limited their applications. Hydroxyapatite (HA) has been shown to enhance the corrosion resistance of Mg alloys. In this study, Mg97Zn1Y2-0.5 wt% HA composite was synthesized and solution treated at 500 °C for 10 h. The corrosion behavior of the composite was studied by electrochemical and immersion tests, while the mechanical properties were investigated by a tensile test. Addition of HA particles improves the corrosion resistance of Mg97Zn1Y2 alloy without sacrificing tensile strength. The improved corrosion resistance is due to the formation of a compact Ca-P surface layer and a decrease of the volume fraction of the LPSO phase, both resulting from the addition of HA. After solution-treatment, the corrosion resistance of the composite decreases. This is due to the formation of a more extended LPSO phase, which weakens its role as a corrosion barrier in protecting the Mg matrix.

Highlights

Biomedical metals and biodegradable polymers are widely used as implants
These four alloys consist of primary dendritic matrix and secondary phase distributed along the grain boundary or in the interdendritic regions
Energy dispersive spectroscopy (EDS) results given in Table 1 indicate that zone 1 is α-Mg solid solution with a relatively low content of Zn and Y, and zone 2 is a phase with a relatively high content of Zn and Y, which can be assigned to Mg12 Z1 Y1 phase with a long period stacking ordered (LPSO) structure as reported in Refs [13,18,26,27] (Table 1)

Summary

Introduction

Biomedical metals and biodegradable polymers are widely used as implants. Medical metals such as stainless steel and titanium alloys can result in stress shielding of the bone and these permanent implants need to be removed by a secondary surgery after healing. Biomedical polymers are degradable but they do not have sufficient mechanical strength. Application of these materials is limited and new biodegradable materials are needed. Mg is non-toxic to the human body and is degradable in the body fluid. The corrosion rate of Mg alloys in the human body is too high. The premature loss of mechanical integrity due to the loss of strength and rapid corrosion rate prevent Mg alloys from clinical applications [7,8]

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