ECAP processing-based improvement of mechanical and corrosion properties of Mg–Li–Y alloys designed for biomedical applications
Jan Dittrich, Michal Knapek, Jozef Veselý, Jiří Kubásek, Jan Bohlen, Stanislav Šašek, Conrado Ramos Moreira Afonso, Peter Minárik
Abstract
A selection of pre-extruded alloys from the Mg–Li–Y system designed for biodegradable orthopedic implant applications was processed by equal channel angular pressing (ECAP). The effect of the resulting microstructure and texture on the mechanical and corrosion performance was investigated. Whereas the single-phase matrix Mg–2Li–2Y, Mg–2Li–4Y, Mg–4Li–2Y, and Mg–4Li–4Y alloys (wt. %) exhibited nearly fully recrystallized fine-grained microstructure, the hcp α-phase of the dual phase hcp + bcc Mg–8Li–1Y alloy exhibited bimodal microstructure. The effect of Li alloying on the activation of non-basal slip systems during ECAP processing gave rise to specific textural components and, during uniaxial tensile and compressive loading, contributed to excellent ductility of the investigated alloys. The fine-grained microstructure led to sufficient strength and low yield asymmetry. The resistance to the initial corrosion attack was partially compromised by the numerous Mg 24 Y 5 precipitates observed in the microstructure of all five alloys. The immersion tests revealed comparatively high corrosion resistance approaching the target values required for internal fixation implants.