The Role of Annealing on Biodegradation Behavior of Mg-Zn-Ca Alloy Prepared from Commercial Mg Sacrificial Anode

Abstract

Magnesium and its alloys offers great potential application for biodegradable implant due to its low corrosion resistance, high biocompatibility, favorable mechanical properties, and young modulus similar to bone. However, there are still many challenges to be solved. In this work, Mg-Zn-Ca alloy were prepared from commercial Mg sacrificial anode, Mg-Ca master alloy, and pure Zn (99%) through casting process. Melting and alloying operations were conducted in a graphite crucible, using a home made melting facility. The influence of annealing treatment on the alloys performance were studied. Microstructure observations of the alloys were conducted using optical and scanning electron microscope equipped with energy-dispersive X-ray spectroscopy. The microhardness of the alloys were evaluated using Brinell hardness indentation. In vitro biodegradation behaviors of Mg-Zn-Ca alloy were evaluated through immersion test in Ringer Laktat solution. The results show that Mg-Zn-Ca alloy fabricated in our work exhibit minimum corrosion rates. Annealing treatment at 300 °C (8 hour, air cooling) alter the microstructure of Mg-Zn-Ca alloy. The microhardness of Mg-Zn-Ca alloys slightly increased from 43 (as cast) to 53 BHN (as annealed). The corrosion rate of the alloys was increased from 8 mm/year (as cast) to 17 mm/year (as annealed). This is suspected due to grain refinement and extensive formation of needle structures causing anodic couples with the matrix.