An investigation on biodegredable properties of micro alloyed az series magnesium alloy

In this study, corrosion and corrosion-related mechanical behaviors of AZ31 alloys and its Ti-micro alloyed version (0,1 wt% Ti, AZ31Ti) in artificial body fluid (SBF) environment were investigated In addition, AZ91 Mg alloy was used for comparison. Microstructure analysis of the samples were performed by using Scanning Electron Microscope (SEM) and X Ray Diffractometer (XRD). Mechanical behaviors were evaluated as microstructure, hardness and tensile tests while corrosion behaviors were evaluated by immersion tests in SBF solution, 37.5±0.5℃ (24, 72 and 336 hours) under dynamic conditions and electrochemical measurements. Hydrogen (H_2) evolution tests were also performed during immersion and electrochemical corrosion tests. Microstructural studies have shown that the β (Mg_17 Al_12) intermetallic phases in the AZ31 alloy are dispersed at the grain boundaries and formed as relatively angular particles and that the dimensions of these β phases are transformed to a smaller size and spherical state with Ti microalloying. In the AZ91 alloy, the β phases were formed in much larger dimensions and network structure at the grain boundaries. Tensile strength and hardness values of AZ31 and AZ31Ti alloys were close to each other, whereas Ti micro alloying showed a considerable increase in the yield strength. The hardness, tensile and yield strength of the alloy increased as the Al ratio increased (i.e AZ91 alloy). Electrochemical test results showed that the corrosion current density (Icor) of the AZ31 alloy was greater as compared to the AZ31Ti alloy, whereas Icor decreased with increasing Al ratio. It has shown that the increase of Al ratio has a more effective role in corrosion probagation. As a result of micro alloying AZ31 alloy with Ti, it has been observed that their mechanical strength is much better in SBF environment. Electrochemical and long-term immersion tests showed that the highest H_2 gas concentration occurred in the AZ91 alloy and the least H_2 gas concentration occurred in the AZ31Ti alloy.