Influence of Equal Channel Angular Processing and Rotary Swaging on the Mechanical and Degradation Properties of WE43 Mg Alloy

Abstract

Magnesium alloy WE43 has high potential for use as biodegradable implants due to its high strength, good corrosion resistance and biocompatibility. In fact, the only two current CE-labelled market available Mg resorbable implants (i.e. MAGNEZIX compression screw and Magmaris scaffold) are both produced from a WE43-based alloy. Nevertheless, to further enhance the use of WE43 in biomedical applications, improvements in mechanical properties and corrosion resistance are desired. Equal channel angular processing (ECAP) and rotary swaging (RS) are two severe plastic deformation (SPD) methods enabling ultra-fine grain structure and subsequently enhanced mechanical properties and reduced degradation rate. Numerous studies have been carried out on the feasibility of processing metals using such methods, but research on use in Mg alloys is limited. In this research, WE43 Mg alloy was processed by extrusion followed by subsequent processing by ECAP or RS. Extensive microscopy was carried out using optical and electron backscatter diffraction (EBSD) and texture measurements were performed using EBSD. Finally, mechanical testing and evaluation of degradation using hydrogen evolution tests were carried out. The results suggest that grain size was significantly reduced by both ECAP and RS resulting in increased strength for both conditions. However, strong basal texture and bimodal grain structure in swaged WE43 resulted in poor ductility and degradation performance, thereby suggesting ECAP as the more promising processing route for enhancing the use of WE43 in biomedical applications.