Design concept and applications of Fe-Mn-Si-based alloys-from shape-memory to seismic response control

Fe-Mn-Si-based alloys exhibit a shape-memory effect associated with deformation-induced γ→η martensitic transformation and its reversion. The γ→ηmartensitic transformation also enhances mechanical properties, such as strength, hardness, wear-resistance and low-cycle fatigue lives of the alloys. In this article, we review fundamental researches on transformation behavior, microstructural and crystallographic characteristics, and functional and mechanical properties of the Fe-Mn-Si-based alloys, and introduce various examples of their practical applications. A special emphasis is placed on their new application as architectural seismic dampers, which were developed based on a new finding of the passive two-way martensitic transformations under cyclic tensile-compressive loading.