Effect of grain size on the mechanical properties of Fe-30Mn-6Si biodegradable alloy

Fe-30Mn-6Si belongs to a multi-functional material and is one of the most attractive alloys for use in engineering applications, such as pipe joints, repairing bone defects in load-bearing areas, etc. The present work focuses on the effect of face-centered cubic (FCC) grain size on the FCC → hexagonal close-packed (HCP) martensitic transformation and mechanical properties of the Fe-30Mn-6Si biodegradable alloy (BA). The specimens which were fully recrystallized with different FCC grain sizes ranging from 8.2 to 15.0 μm were obtained by different annealing treatments following rolling. According to the results, Hall-Petch relationship of the Fe-30Mn-6Si BA was fitted as: σy = 58.9 MPa + 1080.4 MPa•μm1/2 dγ–1/2. The ultra-high K value (1080.4 MPa•μm1/2) indicates that the Fe-30Mn-6Si BA may exhibit ultra-high strength in ultra-fine grain structure. Remarkably, the Fe-30Mn-6Si BA annealed at 900 °C for 5 min overcame the strength-ductility trade-off which resulted in the higher yield strength, ultimate tensile strength and fracture elongation than the alloy annealed at 1000 °C for 5 min despite with a smaller grain size. In addition, compared to Mg- and Zn-based BAs, the Fe-30Mn-6Si BA exhibits superior mechanical properties.