Abstract
Magnesium alloys with rare earth metals are very attractive materials for medical application because of satisfactory mechanical properties. Nevertheless, low corrosion resistance is an obstacle in the use of Mg alloys as resorbable orthopedic implants. The paper presents results of mechanical and corrosion properties of MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. Based on the microscopic observations it was stated that the studied alloys show a dendritic microstructure with interdendritic solute rich regions. The phase analysis reveals an occurrence of α-Mg and Mg2Ca, Ca2Mg6Zn3 phases that are thermodynamic predictions, and stated Mg26Zn59Gd7 phases in MgCa5-xZn1Gdx (x = 1, 2, and 3 wt. %) alloys. The Mg26Zn59Gd7 phases are visible as lamellar precipitations along interdendritic regions. It was confirmed that an increase of Gd content from 1 to 3 wt. % improves ultimate tensile (Rm; from 74 to 89 MPa) and compressive strength (Rc; from 184 to 221 MPa). Moreover, the studied alloys are active in Ringer’s solution. They are characterized by an increase of corrosion potential (Ecorr) of about 150 mV in comparison with values of open circuit potential (EOCP). The best electrochemical parameters (e.g., corrosion current density, icorr, polarization resistance, Rp, and Ecorr) were obtained for the MgCa3Zn1Gd2 alloy.
Highlights
The scientific literature contains many publications on the use of magnesium, calcium, and their alloys as resorbable materials for medical purposes [1–10]
The microstructure of Mg-based alloy with 22 wt. % Gd addition was observed by Vlcek et al
The microstructure of Mg-based alloy with 22 wt. % Gd addition was observed by Vlcek et al [20]
Summary
The scientific literature contains many publications on the use of magnesium, calcium, and their alloys as resorbable materials for medical purposes [1–10]. The problem is the poor corrosion resistance of Ca and Mg alloys [4,8,18]. In this respect, it should be noted that the environmental influence on corrosion affects the application of Mg alloys [19]. The corrosion rate is slow, for example, in pure water, but it is significant in chloride solutions (e.g., Ringer’s solution that simulates the physiological environment) and acid solutions [19–21]. Knowing and understanding magnesium corrosion rate in vivo is an important issue for an application of Mg alloys in medicine [22–28]. To understand the corrosion mechanism of magnesium alloys, it is important to know the corrosion mechanism of pure
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