High degradation rate of Fe-20Mn-based bio-alloys by accumulative cryo-rolling and annealing

- A new Fe5C2 precipitate is achieved after accumulative cryo-rolling and annealing.
- A degradation rate of Fe-Mn-based implant is improved by 4.6 times.
- The high degradation property is related to the occurrence of general corrosion.
- The phase optimization is a possible strategy to prepare bio-Fe implants.

A new strategy of accumulative cryo-rolling (ACR) at liquid nitrogen temperature and annealing was performed to improve degradation rate of Fe-Mn-based implants. Differing from as-cast and ACRed Fe-Mn-based alloys with single-phase austenite, ACRed-annealed sample mainly consists of austenite and non-equilibrium Fe5C2 precipitate. ACR-annealed sample shows a degradation rate of 0.0388 mA·cm− 2, which is 4.6 times higher than as-cast alloy. Pitting corrosion plays a dominant role in both as-cast and ACRed samples. Conversely, some micro-batteries are prone to form among different phase interfaces for ACR-annealed sample, resulting in general corrosion. It reveals that phase optimization is a possible strategy to achieve bio-Fe implants.