Surface treatment and corrosion behaviour of Fe–32Mn–6Si shape memory alloy

Biodegradable shape memory alloys: Progress and prospects

Shape memory alloys (SMAs) have a wide range of potential novel medical applications due to their superelastic properties and ability to restore and retain a 'memorised' shape. However, most SMAs are permanent and do not degrade in the body when used in implantable devices. The use of non-degrading metals may lead to the requirement for secondary removal surgery and this in turn may introduce both short and long-term health risks, or additional waste disposal requirements. Biodegradable SMAs can effectively eliminate these issues by gradually degrading inside the human body while providing the necessary support for healing purposes, therefore significantly alleviating patient discomfort and improving healing efficiency. This paper reviews the current progress in biodegradable SMAs from the perspective of biodegradability, mechanical properties, and biocompatibility. By providing insights into the status of SMAs and biodegradation mechanisms, the prospects for Mg- and Fe-based biodegradable SMAs to advance biodegradable SMA-based medical devices are explored. Finally, the remaining challenges and potential solutions in the biodegradable SMAs area are discussed, providing suggestions and research frameworks for future studies on this topic.

A Potential Biodegradable Metallic Material with Shape Memory Effect Based on Iron

FeMnSi alloys are promising shape memory alloys which have been used for pipe joints but no previous work pays any attention to their biomedical application. Following the outline of the aforementioned development of biodegradable Fe-based alloys, we believe that it is worthwhile to investigate the feasibility of FeMnSi alloy as biodegradable metal candidate, since element Si is widely used in biomedical metallic materials as an alloying element. A shape memory metallic material based on FeMnSi was obtained through classical melting method. The material was analyzed as cast and plastic deformed through rolling concerning materials microstructure (scanning electrons microscopy - SEM), chemical analyses (X-ray analyze by EDAX) and corrosion resistance (or biodegradation rate) in an artificial saliva electrolytic solutions (Fusayama) artificial aerated by linear and cyclic curves determination (potentiometry - VoltaLab).

Shape Memory Effect Improvement and Study of the Corrosion Resistance of the Fe-8Mn-6Si-13Cr-6Ni-12Co Alloy

Fe-8Mn-6Si-13Cr-6Ni-12Co shape memory alloys are characterized by a good corrosion resistance and a modest shape memory effect. Experimental tests of the corrosion resistance of Fe-8Mn-6Si-13Cr-6Ni-12Co have been studied and compared with the Fe-32Mn-6Si alloy using weight loss, free corrosion and polarization resistance tests. The shape memory effect measurement of the Fe-8Mn-6Si-13Cr-6Ni-12Co and Fe-32Mn-6Si alloys has been also tested after 5% of deformation. The results of corrosion experimental tests show that the Fe-8Mn-6Si-13Cr-6Ni-12Co SMA is not very active in the Na2SO4 solution at pH4 at room temperature. In addition, its corrosion resistance is better than the Fe-32Mn-6Si and almost similar to the 316L stainless steel. To improve the shape memory effect of the Fe-8Mn-6Si-13Cr-6Ni-12Co, a thermomechanical treatment has been applied by 8% prestrain in tensile and followed by heat treatment at 1320K for 1 hour. The results show an improvement in the shape memory effect after 5% of deformation in tensile test.