This paper presents a comprehensive study of the effect of the processing by high-pressure torsion (HPT) on the corrosion behavior in Ringer’s solution for two popular bioresorbable magnesium alloys—Mg-1Ca and Mg-1Zn-0.2Ca. Three states were studied for each alloy—the initial homogenized state, the as-HPT-processed state and the state after subsequent annealing at 250 and 300 °C. It is shown that HPT processing results in a very strong grain refinement in both alloys down to a mean grain size of about 210 nm for the Mg-1Ca alloy and 90 nm for the Mg-1Zn-0.2Ca alloy, but their corrosion resistance values differ significantly (by an order of magnitude). The conducted precision scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction studies demonstrate that such a difference in the corrosion behavior is conditioned by a difference in the morphology and origin of the nano-sized particles of second phases, as well as by a change in the electrochemical properties of the “particle–α-Mg” pair. The obtained results are discussed from the perspective of the innovative applications of biodegradable Mg alloys for the manufacture of advanced medical implants and products.

The development of high-performance biodegradable alloys with controllable corrosion rates to be used for manufacturing advanced implants is a hot topic of modern materials science and biomedicine. This work features the changes in microstructure, corrosion behavior and mechanical properties of the Mg-2 wt.%Sr alloy progressively induced by equal-channel angular pressing, high-pressure torsion and annealing. We show that such processing leads to significant microstructure refinement including diminishing grain size, defect accumulation and fragmentation of the initial eutectics. We demonstrate that the application of severe plastic deformation and heat treatment is capable of considerably enhancing the mechanical and corrosion performance of a biodegradable alloy of the Mg-Sr system. The best trade-off between strength, plasticity and the corrosion resistance has been achieved by annealing of the Mg-Sr alloy subjected to combined severe plastic deformation processing.

It is known, that magnesium-based alloys are the appropriate materials to be used as biodegradable metals to produce new-generation medical implants. Magnesium can decompose in the human body during the healing process. If dissolution is controlled, there is no need in additional operation for implant removal after healing completion. Particularly, Mg-Zn-Ca alloys are considered the most appropriate biodegradable metal implants due to their biocompatibility. In the Mg-Zn-Ca alloys, the addition of Zn and Ca as alloying elements can improve the mechanical properties and increase the corrosion resistance compared to pure Mg without affecting biocompatibility. The work covers the study of the structure and mechanical properties of the magnesium Mg-1%Zn-0.2%Ca alloy after severe plastic deformation (SPD). The research of the structure was carried out using scanning and transmission electron microscopy. The study of mechanical properties was carried out by measuring microhardness and tension tests. The study shows that applying the equal channel angular pressing (ECAP) method and additional treatment with the severe plastic deformation (SPD) method to the Mg–1%Zn–0.2%Ca alloy leads to the formation of the ultra-fine grain (UFG) structure with the average grain size of less than 1 micron. The authors identified that, as a result of strong refinement of the magnesium alloy grain structure, the ultimate strength increases twice up to 283 MPa compared to the homogenized state, when the ultimate strength is 125 MPa. At the same time, in the UFG state, the plasticity significantly decreases up to 3 %.

In this paper, we study the strength and fracture mechanism of the cast magnesium alloy Mg-Zn-Ca (1.0 % Zn, 0.2 % Ca) for medical applications after equal-channel angular pressing (ECAP) in comparison with the initial condition (after homogenization annealing).