Session Overview |
Thursday, May 23 |
09:00 |
Computational Design of Mg Alloys with Minimal Galvanic Corrosion
* Pil-Ryung Cha, Kookmin University, South Korea Formation of galvanic cells between constituent phases is largely responsible for corrosion in Mg-based alloys. We develop a methodology to calculate the electrochemical potentials of intermetallic compounds and alloys using a simple model based on the Born-Haber cycle. Calculated electrochemical potentials are used to predict and control the formation of galvanic cells and minimize corrosion. We demonstrate the applicability of our model by minimizing galvanic corrosion in Mg-3wt%Sr-xZn alloy by tailoring the Zn composition. The methodology proposed in this work is applicable for any general alloy system and will facilitate efficient design of corrosion resistant alloys. |
09:30 |
Plasma-based Surface Modifications on Mg Alloys: Focus on Degradation Behavior
Masoud Shekargoftar, Laval University Lab Biomaterials and Bioengineering, Canada Samira Ravanbakhsh, Laval University Lab Biomaterials and Bioengineering, Canada Vinicius Sales de Oliveira, Laval University Lab Biomaterials and Bioengineering, Canada Carlo Paternoster, Laval University Lab Biomaterials and Bioengineering, Canada Frank Witte, Berlin Charité, Germany Andranik Sarkissian, Plasmionique Inc, Canada * Diego Mantovani, Laval University Lab Biomaterials and Bioengineering, Canada Plasma-based processes gained popularity as effective methods for surface modifications. Plasma provides precise controllability through parameters, act symmetrically, and is a versatile tool for modifying material surfaces. The presence of highly energetic species enables the induction of various changes upon collision with the surface. This study aims at using plasma for improving the corrosion resistance of Mg alloys to be used as biodegradable implants. Plasma treatment partially removed the oxide layer and induces reactive species into the surface, responsible for the higher corrosion resistance. Oxygen, nitrogen and hydrogen induce different effects due to the different size of atoms as well as their different interaction with the top oxide layer of the Mg alloy. This led to the different surface morphology after plasma treatment. Oxygen resulted in oxidation of the surface as well as sputtering. Nitrogen atoms caused higher sputtering yield compared to hydrogen. In contrast, hydrogen atoms could penetrate deeper compared to nitrogen. Additionally, hydrogen chemically sputtered the top oxide layer of the Mg alloy. |
09:45 |
Enhancing mechanical properties of biomedical Mg alloy by ultrahigh pressure technology
* Yufeng Zheng, Peking University, China (People's Republic of) Dandan Xia, Peking University Qinggong Jia, Zhengzhou University Shaokang Guan, Zhengzhou University Mg-Ca alloys are one of the most promising materials in the field of bone implant materials. However, the coarse eutectic phase (Mg2Ca) deteriorates material properties. To overcome this problem, the Mg-1wt.% Ca alloy was treated by ultrahigh pressure technology, an alloy with almost α-Mg single phase was obtained. This ultrahigh pressure Mg-1wt% Ca alloy has excellent mechanical properties and corrosion resistance. The maximum compressive yield strength is about 340 MPa and the strain at break is about 27%. The degradation rate of elemental Ca after complete solid solution is about 0.107±0.011 mm/y, and it has a high surface hardness. This is mainly because the UHP solid solution technology can not only effectively refine the grain, but also promote the solid solution of Ca element, eliminating the galvanic coupling corrosion caused by Mg2Ca phase. The high saturated Ca content of magnesium alloy can quickly form a long-term effective barrier layer to block the erosion of solution ions. This technology will have very promising applications in the field of implantable materials. |