Permanent implants are going to be replaced by the implementation of biodegradable magnesium-based implants in fixation of internal bone fractures because of many concerns associated with conventional implants.However,biodegradable magnesium-based biomaterials exhibit higher biodegradation rate and low mechanical properties which are the main challenges.This work aims to almost overcome both disadvantageous by grain refining of a WE43 magnesium alloy containing 93.04 wt％ Mg,4.12 wt％ Y,2.15 wt％ Nd,0.43 wt％ Zr,and 0.26 wt％ La.In this study,the consequences of combined severe plastic deformation (SPD) on the mechanical properties,microstructure,and in vivo degradation behavior of WE43 magnesium alloy were investigated.To do so,WE43 magnesium alloy was chosen and processed through multipass equal channel angular pressing (ECAP) at 330 ℃ for up to four passes followed by an extrusion process.The results showed that higher strength and hardness with minimum ductility less was obtained in the sample processed via two-pass ECAP followed by extrusion.In vivo biodegradation experiments showed higher degradation rate for the unprocessed coarse-grained (CG) WE43 sample.The two-pass ECAP and extruded sample with ultrafine-grained (UFG) structure exhibited the lowest in vivo biodegradation rate besides appropriate mechanical properties.It may be concluded that the WE43 magnesium alloy processed via two-pass ECAP and extrusion could be a very promising candidate for biodegradable implants from both mechanical and biocorrosion viewpoints.