Modeling and experimental study of combined SPD processing of magnesium alloys to obtain rod-shaped samples with ultrafine-grained structure

Over the past decade, considerable attention has been focused on the research and development of magnesium alloys as biodegradable materials with promising mechanical and functional properties for widespread use in medical applications. Along with the selection of the optimal chemical composition, much attention in this work is paid to the development of deformation thermomechanical treatments that allow for varying the microstructure and phase composition in magnesium alloys, which is important for achieving enhanced properties. This work introduces a combined thermomechanical treatment that ensures a high level of mechanical and functional properties in the magnesium alloy. In addition, it produces a long-sized rod required for the manufacture of medical implants on modern CNC cutting machines. The popular magnesium alloy Mg-1 % Zn-0.18 % Ca was selected as the material for research herein. In order to substantiate the design of a processing die-set and modes, an analysis was conducted using the finite element method to establish the deformation behavior of the alloy, including the uniformity of deformation and type of deformed state. The optimal rounding angle of the matrix channels was determined, ensuring uniform deformation during severe plastic deformation using the equal channel angular pressing technique, which allows for the production of long-sized billets from magnesium alloys with enhanced mechanical properties. The experimental study demonstrated that the combined processing of the initial homogenized alloy resulted in the formation of a structure with a grain size of about 215 nm in the UFG alloy Mg-1 % Zn-0.18 % Ca, with a grain size of about 215 nm and the formation of nano-sized particles, which resulted in a substantial enhancement of the mechanical properties of the rods intended for the fabrication of advanced implants in maxillofacial surgery.