Microstructural assessment of the defect tolerance of Cu alloyed steels under cyclic loading
As already shown in the previous project phase, a suitable heat treatment of copper-alloyed steels with low carbon content leads to the formation of copper precipitates, which increase tensile and fatigue strength as well as defect tolerance. Based on these results, the aim of the second project phase is to investigate which microstructural mechanisms lead to this phenomenon.
For this purpose, different heat treatment states of a copper-alloyed, ferritic steel are characterized in fatigue experiments from the LCF to the VHCF regime. In microstructural investigations the interaction between copper precipitates and dislocations is analyzed dependent on the load level and correlated with the fatigue behavior. Furthermore, the investigation of defect tolerance is extended to smaller defects and to the VHCF regime because due to the lower loading the precipitates might show a higher stability, resulting potentially in a different assessment of defect tolerance. The knowledge gained enable an extensive microstructural understanding of the effect of Cu precipitates in steels subjected to cyclic loading, which opens further potentials with regard to this alloy concept.
This project is conducted in collaboration with the Steel Institute of RWTH Aachen University and financially supported by the German Research Foundation (DFG).
