Effects of Dy Addition on the Mechanical and Degradation Properties of Mg–2Zn–0.5Zr Alloy

Abstract

As candidates for biomaterials, magnesium and its alloys have promising properties such as biodegradability and biocompatibility. However, their poor mechanical properties and rapid degradation rate limit clinical application; therefore, solving these issues is essential for practical application. Herein, different contents of dysprosium (Dy) (0, 0.5, 1, 1.5, 2, 3 mass%) are added to the Mg–2Zn–0.5Zr biomagnesium alloy to explore its effect on the mechanical and degradation properties. Assessments are conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), immersion, and electrode chemical experiments. The results indicate that the addition of Dy significantly decreases the grain size, and the second phase is (Mg, Dy)7Zn3 with a body‐centered cubic structure. At a Dy content of 1.5 mass%, grain refinement and second‐phase strengthening result in the alloy having relatively good properties, with an ultimate tensile strength (UTS) = 150 ± 14 MPa, yield strength (YS) = 89 ± 3 MPa, and elongation (EL) = 9.2 ± 0.6%. The addition of Dy promotes the formation of a stable protective film and increases the electrode potential of the Mg matrix, resulting in a degradation rate of 0.89 ± 0.12 mm year−1. The results indicate that the alloy with 1.5 mass% Dy content is a promising candidate for using as a biodegradable material.

Enhancement of mechanical properties and corrosion resistance of Mg–2Zn–0.5Zr–1.5Dy (mass%) alloy by a combination of heat treatment and hot extrusion

“…Furthermore, after extrusion, the grains are significantly refined and the density of grain boundaries increases. As the chemical activity of the grain boundaries is strong, elemental Zn and Dy near the grain boundaries could oxidize and form passivation films on the surface of the alloy, [31] as shown in Figure 11. The passivation films may prevent the corrosive medium from contacting magnesium alloy, thus improving the corrosion resistance of the alloy.…”

“…The passivation films may prevent the corrosive medium from contacting magnesium alloy, thus improving the corrosion resistance of the alloy. [28,31,50,58] In addition, the texture parallel to the (0002) crystal plane exists in the HE alloy. As the surface energy of the (0002) crystal plane is lower than that of (10-10) and (11-20) crystal planes, the breakage degree of the oxide film on the alloy surface is lower, and the protective film structure formed is more stable.…”

“…On this basis, a novel Mg-2Zn-0.5Zr-1.5Dy (mass%) alloy with a low rare earth content was prepared. According to previous research, [31,32] the as-cast Mg-2Zn-0.5Zr-1.5Dy alloy has higher mechanical properties and a lower corrosion rate than the Mg-2Zn-0.5Zr alloy. However, the presence of a second phase in the as-cast Mg-2Zn-0.5Zr-1.5Dy alloy, especially when it is distributed in a reticular structure, can promote the formation and propagation of cracks and is detrimental to its mechanical properties.…”

Corrosion Behavior in Magnesium-Based Alloys for Biomedical Applications

“…The presence of Dy in Mg–Dy alloys can lead to the formation of protective layers. The corresponding oxide product (Dy 2 O 3 ) can effectively increase degradation resistance [ 214 ]. In addition, the Mg 2 Dy phase formed at grain boundaries during non-equilibrium cooling is able to reduce galvanic effects [ 215 ], achieving enhanced corrosion resistance.…”

Laser-Sintered Mg-Zn Supersaturated Solid Solution with High Corrosion Resistance

“…In order to increase their clinical applicability, one issue deserving greater attention is their rapid degradation in vivo [4,5]. In fact, the rapid degradation of Mg is mainly due to its low electrode potential [6,7]. According to electrochemical kinetics, a solid solution of high electrode potential substances (such as Zn, Fe) in a Mg matrix is able to improve the overall electrode potential, thereby enhancing the corrosion resistance and reducing the degradation [8,9].…”