Investigation into the degradation mechanism of Cu-Fe/HA biodegradable composite materials based on experiments and simulations.

The degradation behavior and mechanisms of Cu-Fe/HA composites are investigated in this study, combining experimental analysis with cellular automata simulations to elucidate the synergistic mechanism between Cu and Hydroxyapatite (HA) during the degradation process. The results demonstrate that the corrosion of the Fe matrix exhibits periodic characteristics during corrosion, while the addition of Cu significantly influences the degradation performance of the material. In the early immersion stage (30 days), Cu and Fe form a "Fe-Cu galvanic cell", accelerating the corrosion rate of the sample. In the later immersion stage (180 days), Cu is reduced and deposited on the surface to form a protective film, which instead reduces the degradation rate of samples with higher Cu content (as evidenced by the weight loss rates of 0.04046% and 0.04306% for Cu1-Fe and Cu2-Fe, respectively, compared to only 0.01936% for Cu5-Fe) reflecting a dual role of "initial acceleration followed by subsequent inhibition." The introduction of HA further regulates the degradation process. Its preferential degradation leads to the formation of a porous structure in the sample, thereby increasing the contact area between the solution and Fe and accelerating subsequent corrosion of Fe. Combined with cellular automata simulations, the coupling mechanism between corrosion product exfoliation and dynamic Cu deposition was verified, providing theoretical and experimental support for designing controllable-degradation Cu-Fe/HA composite bone implant materials. The results of biological experiments showed that at an extraction concentration of 12.5 wt. %, the bone cell proliferation rate exceeds 100 %, while the hemolysis rate remains below 2 %, meeting the requirements for biomaterials.