The stacking fault energy (SFE) is a crucial material property that can have a significant effect on the hardening in metals and alloys. As the SFE directly correlates with the splitting width of Shockley partial dislocations it influences the resulting deformation mechanism. By alloying, the SFE and thus the mechanical properties can be adjusted.
Therefore, this work investigates the secondary hardening mechanism in CoCrNi-based alloys. Due to the changed alloy composition in the MP35N (35Co-35Ni-20Cr-10Mo) derivatives and therefore reduced SFE, twin formation is enabled leading to an increased tensile strength for the deformed condition. In addition, a subsequent short-term heat treatment causes a secondary hardening effect by Cr/Mo segregation along planar defects, which further improves the tensile strength up to 2400 MPa for the highest Mo content.
To investigate these segregation effects a correlative approach of transmission electron microscopy (TEM) and atom probe tomography (APT) techniques was used in this work. This results in a better understanding of solute-defect interaction facilitating further tailoring of mechanical properties.