Effect of grain sizes on mechanical properties and biodegradation behavior of pure iron for cardiovascular stent application

ABSTRACT

Pure iron has been demonstrated as a potential candidate for biodegradable metal stents due to its appropriate biocompatibility, suitable mechanical properties and uniform biodegradation behavior. The competing parameters that control the safety and the performance of BMS include proper strength-ductility combination, biocompatibility along with matching rate of corrosion with healing rate of arteries. Being a micrometre-scale biomedical device, the mentioned variables have been found to be governed by the average grain size of the bulk material. Thermo-mechanical processing techniques of the cold rolling and annealing were used to grain-refine the pure iron. Pure Fe samples were unidirectionally cold rolled and then isochronally annealed at different temperatures with the intention of inducing different ranges of grain size. The effect of thermo-mechanical treatment on mechanical properties and corrosion rates of the samples were investigated, correspondingly. Mechanical properties of pure Fe samples improved significantly with decrease in grain size while the corrosion rate decreased marginally with decrease in the average grain sizes. These findings could lead to the optimization of the properties to attain an adequate biodegradation-strength-ductility balance.

Keywords:

• annealing
• biodegradable metal
• cold rolling
• corrosion rate
• iron stent
• mechanical properties

Disclosure of potential conflicts of interest

No potential conflicts of interest were disclosed

Acknowledgments

We are equally grateful to Andre Ferland, Marc Choquette, Maude Larouche, Vicky Dodier, Jean Frenette and Daniel Marcotte, from the Department of Mining, Metallurgical and Materials Engineering, Laval University, Quebec City, Canada, for assistance and technical support.

Funding

We wish to thank the Canadian Commonwealth Scholarship Program for scholarship award to C.S.O. for a PhD training at Laval University. We are also grateful to University of Nigeria, Nsukka, for sponsoring another six months' research stay in the above lab. This research was partially funded by the Natural Science and Engineering Research Council of Canada, the Canadian Institute for Health Research and the CHU de Quebec Research Center.