Influence of Burnishing Process on Microstructure and Corrosion Properties of Mg Alloy AZ31

Abstract

Magnesium (Mg) alloy is an attractive biodegradable implant material in orthopedic fixation applications. Compared with the permanent metallic implant material, such as titanium alloy and stainless, the Young’s modulus of Mg alloys is close to human bone, and it can be gradually absorbed in the human organism. The problems such as stress shielding and secondary surgery operation can be avoided by using Mg alloy. However, the corrosion speed of Mg alloys is too fast for actual medical application. In order to solve this problem burnishing process, which is a kind of surface finishing process, was tried to improve corrosion resistance of Mg alloys in this research. Burnishing experiments were done using a newly developed ball burnishing tool on annealed Mg-Al-Zn alloy AZ31 plates. In order to determine how the parameters of burnishing process affect the microstructure and corrosion properties, the experiments were designed based on Taguchi orthogonal array L9, in which three parameters (burnishing force, tool path interval, and feed speed) are varied at three different levels. For each processing condition, the microstructure near the surface and thickness of layer affected by burnishing process were evaluated by microscope. The experimental results indicated that after the burnishing process the grain size is refined. In addition, corrosion test was carried out and the mass loss of each sample was evaluated. The result shows that burnishing process is effective to improve the corrosion resistance.