Magnesium alloys are among candidate materials for biodegradable implant applications owing to their good mechanical properties and biocompatibility . The purpose of this work was to investigate microstructure, mechanical and corrosion properties, and biocompatibility of ultrafine-grained magnesium alloy WE43 produced by equal-channel angular pressing (ECAP). Route Bc ECAP was conducted using a die with an angle of 120° between the channels, with a stepwise decrease of temperature from the initial 425°C to 300°C at the final, 12th pass. The cumulative equivalent strain the ECAP billets underwent was about 7.6.
As a result of ECAP processing, an ultrafine grain structure with an average grain size of 0.7μm was formed. Furthermore, we observed precipitates of equilibrium phase Mg12Nd with the size as small as 0.3μm. This refinement of the microstructure brought about an improvement of the mechanical properties of the alloy over the as-received condition. The values of the yield strength, YS=260MPa, the ultimate tensile strength, UTS=300MPa, and the tensile elongation, EL=13%, the alloy attained are exceptionally good. This improvement of mechanical characteristics was not achieved at the cost of corrosion resistance, as was demonstrated by electrochemical tests. Rather, the corrosion rate determined by measurements of weight loss and hydrogen evolution were found to be reduced. Biocompatibility assessment by incubation of deformed alloy samples in a suspension of red blood cells, mononuclear leukocytes and mesenchymal stromal cells showed hemolysis deceleration, decreased cytotoxicity and enhanced cell proliferation compared to the non-deformed alloy. It can be concluded that processing by ECAP can be used as a potent way of improving the entirety of the properties relevant to the use of alloy WE43 for medical implants.
The work was supported by the Ministry of Education and Science of the Russian Federation (State Contract N14.A12.31.0001)
 Y.F.Zheng, X.N.Gu, F.Witte, Biodegradable metals, Mater. Sci.Eng. R. 77 (2014) 1–34