Improving In-Vitro Corrosion and Degradation Performance of Mg-Zn-Ca Alloy for Biomedical Applications by Equal Channel Angular Pressing

Magnesium and its alloys have tremendous potential as biodegradable implant materials but finding the right compromise between corrosion resistance and mechanical properties is an ongoing investigation. This study utilized equal channel angular pressing (ECAP) to fabricate Magnesium-ZX 30 alloy with a refined uniform microstructure. ECAP processing via routes Bc and A for up to four passes resulted in the evolution of dynamically recrystallized textured alpha-Mg ultrafine grains with a high fraction of low-angle boundaries. 4Bc and 4A processing via ECAP yielded significant grain refinements of 91.6% and 86.5%, respectively compared to the as-annealed condition. X-ray diffraction verified that the alpha-Mg phase dominated the microstructure as a result of ECAP processing promoting the dissolution of second phases due to the high density of dislocations and vacancies it generated. Electrochemical analysis revealed that ECAP reduced galvanic corrosion and pitting corrosion. Compared to the as-annealed sample, all ECAP-processed conditions displayed a significant decrease in corrosion rates, most notably among them is the 4A condition (97%). Moreover, the surge in grain boundary density and in grain boundary misorientations accelerated the formation of the passivation film, which enhanced the corrosion resistance compared to the as-annealed conditions by 254%, 418% for the 4Bc and 4A processed conditions, respectively. This was corroborated by an immersion test conducted in ringer lactate solution for 360 h. This current work signifies that ECAP processing is capable of producing ZX30 alloy medical implants with high mechanical properties and excellent corrosion resistance that make it suitable for future in-vitro research.