Effect of Ferrite Second Phase on Shape Memory Effect of Corrosion-Resistant Fe-Mn-Si Shape Memory Alloy

At present, Fe-Mn-Si shape memory alloy with high corrosion resistance has become the focus of attention because of its special requirements in some fields. On the basis of Fe-Mn-Si shape memory alloy, a corrosion-resistant shape memory alloy was designed by adding Cr and other alloy elements. The microstructure characteristics and phase ratio control mechanism of the annealed alloy and the influence mechanism of the second phase (ferrite) and ratio on the alloy memory effect are emphatically studied. The results show that ferrite and austenite are evenly distributed at low annealing temperature, and there is thermal-induced epsilon-martensite at the same time. Appropriate thermal-induced epsilon-martensite can strengthen the austenite matrix, and the shape recovery rate is high at this time. With the increase of annealing temperature, the volume fraction and grain size of ferrite increase, the volume fraction of thermal-induced epsilon-martensite and austenite decreases, and the shape recovery rate decreases, but it is beneficial to improve the corrosion resistance. The results indicate that at low annealing temperatures, ferrite and austenite are evenly distributed, along with thermal-induced epsilon-martensite. Appropriate epsilon-martensite enhances the austenite, resulting in a high shape recovery rate. As the annealing temperature rises, the ferrite content increases, while epsilon-martensite and austenite decrease, reducing the shape recovery rate. Thus, controlling ferrite content is crucial for achieving shape memory effect. image (c) 2024 WILEY-VCH GmbH