Research of Dynamic Corrosion Behavior, Microstructure, and Biocompatibility of Mg–Zn–Ca–Zr Alloys in Simulated Body Fluid Solution Induced by Zn Element Addition

Abstract

Herein, the effect of Zn (2,3,4 and 5 wt%) addition on the microstructure, corrosion behavior, and biocompatibility of Mg‐xZn‐0.5Ca‐0.4Zr alloys is discussed by micromorphology, immersion/electrochemical, and cytotoxicity experiments. The results reveal that all as‐cast samples with a duplex morphology consist of Mg7Zn3 phase and α‐Mg matrix. With the addition of Zn element, the quantities of Mg7Zn3 phase increase gradually; while its micromorphology obviously changes from dot‐like to network shape, the average grain size decreases gradually. In addition, corrosion mechanism demonstrates that all as‐cast alloys suffer from microgalvanic corrosion between eutectic Mg7Zn3 and α‐Mg substrate due to potential difference of |ΔE| = 180 mV. However, the strip‐shape Mg7Zn3 contained in the Mg–4Zn–0.5Ca–0.4Zr alloy and compared with dot‐like\network shape phase can effectively hinder the spreading of corrosion from one grain to another, which causes Mg–4Zn–0.5Ca–0.4Zr to exhibit superior corrosion resistance. In addition, the biocompatibility conducted by methyl‐thiazolyl‐tetrazolium method via L929 cells reveals that as‐cast Mg–4Zn–0.5Ca–0.4Zr alloy is confirmed with low hemolysis rate (H% = 2.5%) and excellent proliferation capability (P% > 100%), which suggest that Mg–4Zn–0.5Ca–0.4Zr may be a good candidate for implant application.

Improving Corrosion and Stress Corrosion Cracking Performance of Machined Biodegradable Alloy ZX20 by HF-Treatment

“…The design of the microstructure through alloying, heat treatment, and thermomechanical processing, on the one hand, and the protection of the surface using coatings and surface modification techniques, on the other, represent the two main approaches for enhancing the corrosion performance of biomedical Mg alloys. The optimization of the alloying content aims at controlling the number and composition of secondary phase particles or reducing the electrode potential difference between them and the Mg matrix [9][10][11][12][13][14][15] as well as selection of the optimal parameters of the heat treatments and thermomechanical processes, including extrusion, hot-rolling, equal channel angular pressing, and other severe plastic deformation techniques [16][17][18][19][20][21][22][23]. Various methods for protecting the Mg surface from corrosion, including conversion [24][25][26] and organic coatings [27,28], anodizing and plasma electrolytic oxidation [29,30], surface heat treatment, and plastic deformation [9,31,32], have been proposed so far.…”