Mechanical properties and bio-corrosion behavior of Mg-Zn-Zr alloy influenced by rotary swaging

Abstract

Magnesium alloys have received wide attention for their outstanding biocompatibility and an elastic modulus that is close to human bone. Whereas their mechanical and corrosion properties are poor, which need to be improved by alloying, processing and heat treatment processes, so as to expand their applications in the field of biomaterials. For the study, Mg-2.98 wt% Zn-0.50 wt% Zr alloys were produced by rotary swaging and some of the alloys were T2-treated at 250 ℃ for 1 h. The microstructure, mechanical properties, bio-corrosion behavior, and biocompatibility of the experimental alloys were evaluated using optical and scanning electron microscope, X-ray diffraction, tensile, electrochemical, immersion and cytotoxicity tests. The results indicated that the experimental alloys had good biocompatibility. After rotary swaging, the homogeneous alloy grains were significantly refined, the presence of twins could be observed obviously, and the alloy exhibited superior mechanical properties (with a yield strength of 274 MPa, an ultimate tensile strength of 316 MPa and an elongation of 22.9%) and corrosion rate (0.539 mm/y in electrochemical test and 0.31 mm/y in immersion test). After further T2-treated, the yield strength and ultimate tensile strength of the alloy decreased by 26% and 20%, respectively, and the elongation increased by only 6.6%. Additionally, the corrosion rate increased by 17.8% in the electrochemical test and by more than 14 times in the immersion test. Such changes in properties are closely associated with the disappearance of twins.