Regulating mechanical properties and degradation behavior of biodegradable Zn-0.6Mg alloy via ECAP plus cold rolling

Binary Zn-Mg alloys have great potential as biodegradable implants due to their good biological safety and moderate degradation rates. Herein, a new combined process of ECAP plus cold rolling of as-cast Zn-0.6Mg alloy was developed to address its application problem of insufficient mechanical properties and serious localized corrosion. Cold rolling process can break the eutectic phase and refine grains, while deformed grains were dominant with a lot of dislocations. 8-pass ECAP process can refine grains by recrystallization, and the grains were equiaxed with less dislocations. The strength and ductility were greatly improved after cold rolling (CR) or ECAP processing compared with that of as-cast alloy, but the strength still cannot meet the requirement of orthopedic implant materials. After 8-pass ECAP+CR75% (ER) processing, the strength was further improved, which benefited from fine grain strengthening, second phase strengthening, and strain strengthening mechanisms. Tensile yield strength (Sigma YS), ultimate tensile strength (Sigma UTS), and fractured elongation of ER alloy were 301.2 MPa, 411.8 MPa, and 28.5%, respectively, which can meet the requirement of orthopedic implants. The eutectic phase fragmentation and grain refinement caused by cold rolling and ECAP process can reduce the galvanic corrosion tendency of the Zn-0.6Mg alloy. The corrosion resistance was further improved after 8-pass ECAP+CR75% processing with the degradation rate of 0.025 mm/y, and the alloy tended to corrode uniformly.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

A combined process of cold rolling and equal channel angular pressing (ECAP) was developed to improve the mechanical properties and localized corrosion of Zn-0.6Mg alloy for biodegradable implants. After cold rolling and ECAP processing, the alloy exhibited significantly improved strength and ductility compared to the as-cast alloy, with the alloy processed by 8-pass ECAP+CR75% (ER) showing the best mechanical properties. The eutectic phase fragmentation and grain refinement caused by cold rolling and ECAP process reduced the galvanic corrosion tendency of the alloy, resulting in improved corrosion resistance.