Memory-Steel Fatigue - Influence of precipitates on stress relaxation and fatigue behavior of prestressed Fe-based Shape Memory Alloys

Due to their inherent properties and comparatively low costs, iron-based shape memory alloys are highly promising for applications as prestressing elements in civil engineering. However, up to now the applicable stress levels are limited and time-dependent relaxation of the prestressing elements occurs and is shown to be enhanced by superimposed cyclic loading. Initial experiments showed that nanoscale precipitates can significantly increase the prestressing level of such alloys. However, there are no studies on how nanoscale precipitates affect the relaxation behavior and fatigue properties of such alloys. Therefore, the influence of nanoscaled precipitates on relaxation behavior, as well as on the fatigue behavior of iron-based shape memory alloys will be systematically investigated in the proposed project. An Fe-Mn-SI-Cr-Ni-VC alloy and an Fe-Mn-Al-Ni alloy will be investigated as model alloys in order to derive cross-material influencing factors of the precipitates on the resulting properties.

Research centers:

• Institute for Steel Construction (Leibniz Universität Hannover)
• Institute of Materials Engineering – Metallic Materials (Universität Kassel)