A newly developed Mg-Zn-Gd-Mn-Sr alloy for degradable implant applications: Influence of extrusion temperature on microstructure, mechanical properties and in vitro corrosion behavior

Abstract

The object of this study is to investigate the influence of extrusion temperature on the microstructure, mechanical properties and in vitro corrosion behavior of Mg–2Zn–1Gd–0.4Mn–0.1Sr (ZGMS) alloy. The results show that as–extruded ZMGS alloy mainly contains α–Mg and Mg3Zn3Gd2 (W) phases, and the W phase is uniformly distributed in the Mg matrix. With decreasing extrusion temperature, the grain size is refined, and numerous nano–sized W particles dynamically precipitate during extrusion process. The mechanical properties of as–extruded experimental alloy is significantly improved with decreased extrusion temperature.This is owing to the effects of grain boundary strengthening, precipitation strengthening and dislocation strengthening. The experimental alloy exhibits the lowest corrosion rate and relatively uniform corrosion after extrusion at 360 °C. The corrosion products layer are mainly composed of Ca10(PO4)6(OH)2, Ca3(PO4)2 Mg(OH)2 and MgHPO4. The as–extruded alloy owns excellent mechanical properties (yield strength of 206.3 MPa ultimate tensile strength of 261.1 MPa and elongation of 27.3%) and corrosion rate (0.17 mg/cm2/day) after extruded at 360 °C. The alloy presents tremendous potential in degradable implant applications. Additionally, the relationship between microstructure and corrosion behavior was systematically discussed.