Abstract: Biodegradable magnesium (Mg) alloys have received much attention due to their biocompatibility and biodegradation. In this study, to uncover the effects of grain morphologies, including grain size and distribution on mechanical and corrosion properties, biodegradable Mg-2.1Nd-0.2Zn-0.5Zr (wt.%) (denoted as JDBM) alloy mini-tubes for stent application with three typical microstructures were achieved successfully by adjusting drawing parameters. Samples with the bimodal structure exhibit the highest strength-ductility balance attributed to the combined effects of fine grains and coarse grains, but show the fastest corrosion rate of about 1.00 ± 0.136 mm/year mainly due to the formation of micro galvanic couples between coarse and fined grains. Samples with fine equiaxed grains show the lowest corrosion rate of about 0.17 ± 0.059 mm/year, as well as uniform corrosion mode and mechanical properties of yield strength (YS) 256 ± 5.7 MPa, ultimate tensile strength (UTS) 266 ± 3.8 MPa, and elongation to failure (EL) 13.5% ± 1.8%, attributed to the high-density grain boundaries. Samples with coarse equiaxed grains exhibit medium corrosion resistance and mechanical properties of about 175 ± 4.8 MPa, 221 ± 4.0 MPa, and 21.53% ± 4.1%. Considering the mechanical and in vitro corrosion properties, biodegradable JDBM alloy implants are recommended to be composed of fine equiaxed grains, which can be used as microstructural targets for fabrication and processing.

Key words: Magnesium alloy, Grain morphology, Corrosion, Mechanical properties, Mini-tubes