# Influence of Noble Metals on the Microstructure and Properties of Biodegradable Mg-Nd-Zr Alloy  
[PERSON]  
1 Faculty of Engineering and Physics, National University Zaporizhia Polytechnic,  
69063 Zaporizhia, Ukraine; [EMAIL_ADDRESS] (V.G. ); [EMAIL_ADDRESS] (S.B)  
[PERSON]  
1 Faculty of Engineering and Physics, National University Zaporizhia Polytechnic,  
69063 Zaporizhia, Ukraine; [EMAIL_ADDRESS] (V.G. ); [EMAIL_ADDRESS] (S.B)  
[PERSON]  
1 Faculty of Engineering and Physics, National University Zaporizhia Polytechnic,  
69063 Zaporizhia, Ukraine; [EMAIL_ADDRESS] (V.G. ); [EMAIL_ADDRESS] (S.B)  
[PERSON]  
2 Division of Metallic Systems, Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47,  
04001 Kosice, Slovakia; {[EMAIL_ADDRESS] (I.P. ); [EMAIL_ADDRESS] (V.E.) [PERSON]  
2 Division of Metallic Systems, Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47,  
04001 Kosice, Slovakia; {[EMAIL_ADDRESS] (I.P. ); [EMAIL_ADDRESS] (V.E.) One of these materials may be magnesium, which is a natural element in the body, and its bioresorption products are characterized by high biocompatibility [11; 12; 13]. These properties make magnesium attractive for use in orthopedics and traumatology [14; 15; 16]. However, the main limitation of its use is low mechanical properties [3; 17; 18]. The solution to the problem is the use of Mg-based alloys, which have a higher level of mechanical properties and an elastic modulus comparable to that of bone tissue [19]. In this regard, the research and development of biodegradable Mg-based alloys is a promising direction in biomaterials engineering. The use of implants made of biodegradable Mg-based alloys eliminates the additional operations for removing them and the complications associated with the long-term presence of an implant in the bone. When choosing the chemical composition of a biodegradable alloy, it is important that the biocorrosion products are metabolized in the body, bioabsorbed and not toxic. Previous studies [16] established the requirements for the development of a biodegradable Mg-based alloy intended for implants in osteosynthesis:  
* Required level of mechanical properties is as follows: ultimate tensile strength (UTS) \(\geq\)150 MPa, total elongation (TE) \(\geq\) 3.1%. This is comparable to the properties of bone tissue and ensures its reliable fusion up to complete consolidation of the fracture (3 months);
* No toxic effects on the body. According to [20], the most widely used alloying elements in magnesium-based compositions are zinc, calcium, zirconium, manganese, silver, and rare earth elements. Zinc decreases the corrosive effects of some common impurities in Mg-based alloys such as iron and nickel. Additionally, a deficiency of zinc in the human body can result in serious illnesses; therefore, Zn also acts as a bioactive element in degradable magnesium alloys. Manganese improves mechanical properties and alloy viscosity at quantities below 2 wt.%. Calcium possesses grain refining effect and strengthening of grain boundaries. Due to Laves-type phases with Mg\({}_{2}\)Ca composition, creep resistance of magnesium alloys can be improved [21]. The addition of Zr and rare earth elements, namely yttrium, neodymium and cerium, also leads to grain refinement and increases the strength of magnesium alloys [22]. The toxicological and physiological properties are other important issues regarding magnesium itself and the main alloying elements for biodegradable magnesium alloys. According to data summarized in [20; 23], the distinctive properties of each element are as follows. * Magnesium has a positive influence on metabolism, synthesis of protein, and cell proliferation. It promotes the stabilization of RNA and DNA, regulates protein activity and also affects cellular reactions;
* Zinc is important for the immune system. * Calcium is mainly concentrated in bones.