Microstructures, Mechanical Properties, and Corrosion Behavior of As-Cast Mg–2.0Zn–0.5Zr–xGd (wt %) Biodegradable Alloys

Abstract

The Mg–Zn–Zr–Gd alloys belong to a group of biometallic alloys suitable for bone substitution. While biocompatibility arises from the harmlessness of the metals, the biocorrosion behavior and its origins remain elusive. Here, aiming for the tailored biodegradability, we prepared the Mg–2.0Zn–0.5Zr–xGd (wt %) alloys with different Gd percentages (x = 0, 1, 2, 3, 4, 5), and studied their microstructures and biocorrosion behavior. Results showed that adding a moderate amount of Gd into Mg–2.0Zn–0.5Zr alloys will refine and homogenize α-Mg grains, change the morphology and distribution of (Mg, Zn)3Gd, and lead to enhancement of mechanical properties and anticorrosive performance. At the optimized content of 3.0%, the fishbone-shaped network, ellipsoidal, and rod-like (Mg, Zn)3Gd phase turns up, along with the 14H-type long period stacking ordered (14H-LPSO) structures decorated with nanoscale rod-like (Mg, Zn)3Gd phases. The 14H-LPSO structure only exists when x ≥ 3.0, and its content increases with the Gd content. The Mg–2.0Zn–0.5Zr–3.0Gd alloy possesses a better ultimate tensile strength of 204 ± 3 MPa, yield strength of 155 ± 3 MPa, and elongation of 10.6 ± 0.6%. Corrosion tests verified that the Mg–2.0Zn–0.5Zr–3.0Gd alloy possesses the best corrosion resistance and uniform corrosion mode. The microstructure impacts on the corrosion resistance were also studied.

Corrosion decomposition and mechanical behaviors of As‐cast Mg–xZn–Zr alloys

“…Compared with frequently used decomposable Mg-RE-Zr and Mg-Al-Zn-RE alloys, [22,23] higher mass loss and corrosion rate in chloride environment are expected to be achieved for Mg-Zn-Zr alloy. This is due to the fact that the addition of rare earth (RE) in the alloys can enhance their corrosion potentials and decrease the corresponding corrosion current densities.…”

Enhancing the Corrosion Resistance Performance of Mg-1.8Zn-1.74Gd-0.5Y-0.4Zr Biomaterial via Solution Treatment Process

“….06 g/L KH 2 PO 4 , and 0.06 g/L MgSO 4 •7H 2 O) [7] and went on for 3600 s at 37 • C. After 3600 s stabilization, the polarization curve was measured from −250 mV to +400 mV relative to the value of OCP vs. SEC at a scanning rate of 1 mV/s. The self-corrosion potential (E corr ) and corrosion current density (I corr ) were calculated by Tafel extrapolation.…”

“…To overcome the rapid corrosion rate in the service period, a lot of studies have been done to improve the performance of corrosion, such as micro-alloying [6][7][8], surface modification and composites [9,10]. Alloying is one of the most effective methods.…”

“…Gadolinium (Gd), as rare earth element, is suitable for biomedical material [11,13]. The addition of Gd element can markedly ameliorate both the corrosion resistance and mechanical properties [7]. When the ratio of Zn/Gd is high, Mg 3 Zn 6 Gd phase, cubic Mg 2 Zn 3 Gd 2 phase and binary Mg-Zn phase are the mainly phases in Mg 95.9 Zn 3.5 Gd 0.6 (at%) alloy [14].…”

Effect of Zn addition on the microstructures and mechanical behaviors of As-cast Mg-2.5Y-1Ce-0.5Mn alloy

“…In the point of plastic instability, the Alloy IV shows the largest strain hardening ability while the Alloy I exhibits the lowest strain hardening ability. Figure 6 compares the ultimate tensile strength s UTS ( ) and elongation d ( ) of present as-cast Mg-2.5Y-1Ce-0.5Mn-xZn (x=0, 1, 3, 5 wt%) alloys with the published results of tensile tests in other as-cast Mg-RE or Mg-RE-Zn alloys [10,16,[19][20][21][22][23][24][25][26][27][28][29][30]. It is notable that the other as-cast alloys exhibit various s UTS values in a wide range while most of their d values are lower than 8%.…”