In recent years, Mg alloys have attracted increased attention for biomedical application owing to their good biodegradability, biocompatibility, and biomechanical properties. However, rapid corrosion is still one of the most common limitations for their implanted application. In this work, the microstructure and corrosion behavior of the solution- and aging-treated Mg-xGd-1Zn-0.4Zr (x = 3, 6, and 9 wt%, denoted as GZ31K, GZ61K, and GZ91K, respectively) alloys were studied using optical microscope (OM), scanning electron microscope (SEM), immersion tests, electrochemical tests, and quasi in situ corrosion method. The results show that block Gd-rich precipitates and needle-like Zr-Zn-rich precipitates are formed as well as α-Mg matrix. With the increase in Gd content, the precipitates increase and the grain size first reduces and then increases. Corrosion experiment results show that the GZ61K alloy has the best corrosion resistance and the GZ91K alloy shows the highest corrosion rate among the three alloys in simulated body fluid (SBF). It is found that α-Mg is preferentially corroded and the precipitates have better corrosion resistance as compared to the α-Mg matrix. The GZ61K alloy with the corrosion rate of 0.227 mm/y in SBF shows a promising prospect for biomedical application.

Generally, excellent mechanical properties of Mg alloys are desired, but their rapid degradation properties are seldom utilized. Petroleum fracturing techniques are required to take full advantage of this rapid degradation. Therefore, we have prepared an as-extruded Mg–6.0Gd–1.2Cu–1.2Zr (wt.%) alloy and treated it with peak aging to analyze its potential as a degradable fracture ball. The results show that the as-extruded alloy mainly consists of an α-Mg matrix, second phase, and large elongated α-Mg grains (LEGs). After aging, the LEGs undergo static recrystallization, which improves the mechanical properties of the alloy, and a lamellar long period stacking ordered (LPSO) phase is observed. Under simulated underground temperature conditions (93 °C), the ultimate tensile strength and elongation of both as-extruded and as-aged alloys are over Ȧ MPa and 11.1%, respectively, and the ultimate compressive strength and elongation of both alloys are over 336 MPa and 16.9%, respectively. The corrosion rate of the as-extruded alloy in 3 wt.% KCl solution at 93 °C reaches 1660.8 mm/y by mass loss test, and that of the as-aged alloy increases to 1955.1 mm/y. The atomic force microscope analysis result confirms that the second phase shows the highest corrosion potential, followed by the lamellar LPSO phase and α-Mg matrix. The as-extruded and as-aged Mg–6.0Gd–1.2Cu–1.2Zr alloy with good mechanical properties and a high corrosion rate in this work shows promising potential for degradable fracturing ball applications.

No abstract