Machining characteristics of biodegradable Zn-2Mg-0.1Cu alloy under varying cutting conditions

Biodegradable implant materials hold significant potential by degrading within the body after fulfilling their intended function. The advantages of such materials emphasize the need for increased diversity in functional biomaterials and further research in this area. This experimental study aims to develop and investigate Zn-2Mg-0.1Cu alloys and evaluate their machinability. To develop Zn-2Mg-0.1Cu alloys, high-purity elements were melted at 565°C under an argon atmosphere and cast into preheated steel molds. Homogenization at 350°C for 16 hours followed by quenching with iced water was applied to ensure uniform microstructure. The samples were examined using microstructural analysis, and mechanical tests were conducted to assess the effects of Cu addition. In the drilling process, the feed rate was initially kept constant at 200 mm/min, while the spindle speed was varied (2000, 4000, and 6000 rpm) to study the effects of spindle speed on the drilling results. Then, when the spindle speed was fixed at 5000 rpm, the feed rate was adjusted (150, 250, and 350 mm/min) and the effect of feed rate was studied. Drilling characteristics—including thrust force, chip formation, burr formation, surface morphology, and roughness—were analyzed to evaluate machinability. The addition of Cu led to secondary phase formation within the structure, increasing the hardness of the samples. The thrust force decreased by 4.5% at 2000 rpm, 6.3% at 4000 rpm and 1.4% at 6000 rpm in Cu added samples. At lower spindle speeds, the increased hardness from Cu addition resulted in shorter chip lengths. Additionally, Cu addition provided a more consistent and reduced surface roughness along the hole surface. The lowest average surface roughness was 0.446 µm for Zn-2Mg and 0.267 µm for Zn-2Mg-0.1Cu at 200 mm/min feed rate and 6000 rpm spindle speed, 0.385 µm for Zn-2Mg and 0.271 µm for Zn-2Mg-0.1Cu at 5000 rpm spindle speed and 150 mm/min feed rate. In summary, the analysis of these data indicates that Cu addition improved the machinability of the alloy.