What are the surface modification methods of magnesium alloys?

?Where can magnesium alloys be used as medical materials

Medical magnesium alloys are known as the third-generation biomedical materials as degradable medical materials. Magnesium alloys have high strength, toughness and processing properties, good absorbability and biocompatibility, and orthopedic implants have a density and elastic modulus close to the bone. Medical magnesium alloys also have a controllable corrosion rate. Currently, they are mainly used in bone fixation materials, porous bone repair materials, dental implant materials, oral repair materials, and cardiovascular stents.   

1. Magnesium alloys as bone fixation materials: 

magnesium alloy bone plates, magnesium alloy bone nails, and other fixation materials for bone damage are closer to the elastic modulus of human bone than other metal biomedical materials, have strong toughness, and biocompatibility, and are more efficient. Effectively reduce the stress shielding effect.

2. Magnesium alloys as porous scaffolds for bone tissue engineering: 

The porosity of bone tissue engineering scaffolds is very significant. Porous bioceramics and polymer scaffolds are often used, but their mechanical properties are poor. Studies have shown that magnesium alloys meet the requirements of porous scaffolds for bone tissue, have good mechanical properties, and have good biocompatibility, biodegradability, and absorbability. Therefore, magnesium alloys have the conditions to become an ideal scaffold material for bone tissue replacement. But at the same time, magnesium alloy stents will be explained at a very fast speed in human body fluids, and hydrogen is generated, which is also a problem that needs to be studied and solved.

3. Magnesium alloys are used as stent materials for coronary implants: 

the good mechanical properties, degradability, and absorbability of magnesium alloys are also used to replace other biomedical materials.

4. Other implant materials of magnesium alloys: 

Since magnesium is an essential element in the human body, magnesium alloys can have good corrosion resistance by changing the composition and surface treatment of magnesium alloys. Materials and orthopedic materials, etc., can also be considered as implant materials using magnesium and magnesium alloys.

What are the surface modification methods of magnesium alloys?

The corrosion resistance of magnesium alloys is poor, and the pH value in the human body is about 7.4. The corrosion of magnesium alloys as implant materials will accelerate in human body fluids. In addition, magnesium is a significant element of the human body, but absorbing too many magnesium ions is also harmful to the human body. Therefore, the research on the nature of corrosion and surface modification technology of magnesium alloys is the key to the application of magnesium alloys in biomedicine. There are many modification methods for magnesium alloys, mainly through physical, chemical, biological, and other technologies to improve the surface properties of the material, thereby effectively improving the compatibility of biological materials with the human body.

1. Improve the corrosion resistance of magnesium alloys

1.1 Improve the purity of magnesium alloys:reduce the content of impurities in the metal, which can effectively improve the corrosion resistance of the alloy.

1.2 Synthetic protective film or coating: mainly includes chemical conversion film and organic film. The chemical conversion coating layer is often treated with chromate, which is toxic and harmful to human health and is not suitable for surface treatment of medical magnesium alloy materials. Later, a surface treatment process based on permanganate, soluble silicate, sulfate, hydroxide, etc., was developed. The rare earth conversion technology was used to form a protective film on the surface of magnesium alloy, which significantly improved the performance and corrosion resistance of magnesium alloy. The organic film layer can only protect the magnesium alloy material for a short time and cannot be used as a protective coating for a long time.

1.3 Adopt the rapid solidification process: rapid solidification can reduce the harmful effects of impurities and generate a protective vitreous film, thereby improving the corrosion resistance of the material.

1.4 Surface modification techniques such as ion implantation and laser treatment: Ion implantation refers to the accelerated injection of high-energy ions into a solid surface under vacuum conditions. This method can implant almost all ions. Corrosion-resistant elements can be injected to improve the corrosion resistance of magnesium alloys. Laser treatment can change the metal surface to form a metastable structural solid solution, enabling rapid solidification of the alloy surface.

1. Surface Morphology and Biocompatibility of Magnesium Alloys

The better compatibility of magnesium alloy biomaterials implanted in the human body because the smooth surface can reduce the transformation of coagulation factors.

2. Surface modification of biomedical materials

Normal human organs can be naturally accepted and controlled by the human body system, but the biological magnesium alloy material implanted in the human body is easily regarded as a foreign body by the human body system, resulting in a rejection reaction. The rejection reaction can be avoided by modifying the surface of magnesium alloy materials. Methods include planting endothelial cells on the surface of biological magnesium alloy materials and coating albumin coating.

Compared with traditional alloys, a major advantage of magnesium alloys is their biodegradability, which can provide mechanical support for bones and tissues at the initial stage of implantation. After that, magnesium alloys are gradually degraded under the corrosive action of body fluids and absorbed by the human body, eliminating the need for removal. Secondary surgery for implants. Therefore, magnesium alloys have broad application prospects in the field of biomedicine. However, magnesium alloys corrode too fast in a fluid body environment, which may lead to premature failure of the implant. Therefore, how to improve the corrosion resistance of magnesium alloys is one of the key research directions in the field of materials. For example, the corrosion resistance of magnesium alloys can be improved by using higher purity raw materials, combined with large plastic deformation, rapid solidification, reasonable heat treatment, and surface treatment; using deformation process and heat treatment to control the grain size of the alloy and the size of the secondary precipitation phase and distribution, thereby regulating the failure mode of magnesium alloys. Through the use of multiple means, the performance of magnesium alloys can meet the requirements of the implanted devices to be developed.