Microstructure and properties of biodegradable Zn-0.8Mn-0.5Cu-0.2Sr alloys processed by ECAP

In recent years, Zn alloys had been regarded as biomedical materials with good biocompatibility and biodegradability. However, the mechanical properties of Zn alloys were often not sufficient for the ideal orthopedic internal fixation implant. In order to improve the comprehensive mechanical properties of Zn alloys by strengthening and toughening, equal channel angular pressing (ECAP) method and Bc route were applied to process Zn-0.8Mn-0.5Cu-0.2Sr alloys. Meanwhile, the effects of multi-pass ECAP on mechanical properties, corrosion behavior and microstructure were systematically investigated. As a result, ECAP could significantly refine the grain sizes of the as-cast Zn-0.8Mn-0.5Cu-0.2Sr alloys. Only after 2 passes, the average grain sizes of the Zn-0.8Mn-0.5Cu-0.2Sr alloy could be refined from 54.04 μm in as-cast to 1.20 ± 0.76 μm. In addition, the increase of ECAP passes promoted the precipitation of MnZn13 phase and reduced texture strength, which affected the strength and ductility. The UTS of the 2P and 4P alloys were 337.6MPa and 320.4MPa, respectively. And as ECAP passes increased from 2 to 8, the EL gradually increased from 24.9% to 46.3%. After ECAP, the corrosion rates of the Zn-0.8Mn-0.5Cu-0.2Sr alloys increased. The corrosion rates of the 2P and 4P alloys measured by the weight loss method were about 0.022mm/year and 0.019mm/year. Thus, Zn-0.8Mn-0.5Cu-0.2Sr alloy was expected to be a promising biodegradable material. Meanwhile, ECAP could be an effective avenue to achieve high comprehensive mechanical properties and suitable corrosion rates.