Effect of multi-pass multidirectional forging on microstructure and corrosion behavior of Zn-1Fe biodegradable alloy

Multi-pass multi-directional forging (MDF) was employed to alter the microstructure and enhance the corrosion resistance of Zn-1Fe alloy. The findings indicate that, the MDF refined the irregularly-shaped coarse primary FeZn₁₃ intermetallics and promoted their uniform distribution within the alloy matrix. Compared to the as-cast state, the first, third, and fifth passes of the MDF reduced the average size of FeZn₁₃ particles to 27.5±15.5 μm, 8.8±5.4 μm, and 7.5±5.1 μm, indicating reduction of about 71%, 85%, and 88%, respectively. The MDF notably enhanced the distribution of FeZn₁₃ particles within the matrix, with their number density increasing from 134±106 particles/mm² in the as-cast microstructure to 632±207, 776±170, 1146±265, and 1301±294 particles/mm², in one-pass, two-pass, three-pass, and five-pass MDFed alloys, respectively. Concerning corrosion characteristics, the MDF enhanced the corrosion resistance of the alloys in comparison to that of the as-cast alloy. The two-pass MDFed sample exhibited corrosion resistance that was double that of the as-cast one. However, the corrosion resistance of the five-pass alloy was merely 1.2 times greater than that of the as-cast alloy. This was ascribed to the formation of microcracks within the alloy’s microstructure during excessive passes.