Low-Temperature Mechanical Behavior of Fe-SMA for Structural Damping

Abstract

Iron-based shape memory alloy (Fe-SMA) is an emerging class of material having a great potential for civil engineering, especially seismic engineering applications. However, the behavior of Fe-SMA strongly depends on temperature-sensitive martensitic transformation, and thus the influence of temperature on the behavior of Fe-SMA should receive particular attention. The current study experimentally investigates how temperature variation affects the mechanical properties, including monotonic tensile strength, low cycle fatigue (LCF), and impact toughness, of Fe-SMA (Fe-17Mn-5Si-10Cr-5Ni in wt%), with a particular focus on its low-temperature behavior. Specifically, the considered temperatures used for conducting monotonic tensile and LCF tests were −40°C, −10°C, and 20°C, whereas the range of temperature for impact toughness tests was from −100°C to 20°C. Additional tests were performed on S30408 stainless steel and conventional Q355 structural steel for comparison purposes. The experimental results suggest that low temperature leads to increased strength and reduced ductility of Fe-SMA. The impact toughness of Fe-SMA is comparable with that of S30408 steel, exhibiting ductile fracture characteristic observed even at −100°C. Fe-SMA outperforms conventional steels with an evidently greater LCF life given the considered temperature variation; although, its LCF life decreases at lower temperatures due to the inhibited reversible martensite transformation. This study also provides a set of practical parameters that facilitate constitutive modeling and strain-based fatigue life prediction of Fe-SMA under various temperatures.