Effect of temperature on fracture behavior of Fe-20Mn-5.5Si-8.5Cr-5.5Ni shape memory alloys: An in-situ observation

Iron-based shape memory alloys (Fe-SMAs) have great applied potential to large-scale structures in civil engineering. However, the fundamental fracture behavior and underlying physical mechanism, which are crucial for evaluating the service reliability of such alloys, have received little attention. In this work, an Fe-20Mn-5.5Si8.5Cr-5.5Ni SMA is prepared, and its fracture behavior at different ambient temperatures (298-573 K) is studied by in-situ electron back scattering diffraction (EBSD). It is found that intergranular fracture is more likely to occur than transgranular fracture. Dislocation slip near the crack tip occurs before martensite transformation (i. e., plasticity-induced transformation), and such martensite transformation becomes more and more difficult with the increase of temperature. The dislocation slip-based plasticity contributes more to the shielding effect than the plasticity-induced transformation. As increasing the temperature, the change of the contributor to shielding effect (from both dislocation slip-based plasticity and plasticity-induced transformation to dislocation slip-based plasticity) and the increase of the activity of dislocation slip lead to the increase of toughness and fracture resistance. The temperature-dependent fracture behavior and underlying mechanism of Fe-20Mn-5.5Si-8.5Cr5.5Ni SMA are reported for the first time in this work, which will provide reference for the application and theoretical modeling of Fe-SMA building materials.