The innovative heat treatment concept of “Quenching and Partitioning” (Q&P) enables the production of high-strength martensitic steels with high ductility. Residual austenite is stabilized in the partitioning process by carbon diffusion. This enables the strain-induced phase transformation from austenite to martensite and increases the ductility without reducing the strength. So far, little research has been done on the application of the Q&P process on martensitic stainless steels and their related corrosion resistance. The present work supplements the first investigations by Yuang and Raabe with important material-technical parameters as well as the achievable corrosion resistance. The Q&P heat treatment offers enhanced mechanical properties and a higher corrosion resistance in comparison to the conventional quenching and tempering heat treatment.

Over the last years heat treatment concept of “quenching and partitioning” (Q&P) has reached popularity for its ability to precisely adjust material properties to desired values. Mostly, Q&P process are applied on tailor-made materials with high purities or prototype alloys. The research in hand presents the whole routine of how to investigate the potential of a commercial 0.54C-1.45Si-0.71Mn spring steel in terms of Q&P heat treatment from lab scale in dilatometer measurements to widely used inductive heat treatment on larger scale. In order to obtain the small process window for this material we were focusing on the interplay of the formed microstructure and the resulting mechanical properties in hardness measurements, compression tests as well as tensile tests. After full austenitizing, three different Q&P processing routes were applied. Microstructural analyses by optical microscopy, Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD) exhibit a condition with 6.4% and 15% volume fraction of fine distributed retained austenite. Interestingly, the 15% of retained austenite developed during the partitioning heat treatment. Contradictory to our expectations, tensile and compression testing were showing that the 6.4% condition achieved improved mechanical properties compared to the 15% retained austenite condition. The remarkable conclusion is that not only volume fraction and fine distribution of retained austenite determines the potential of improving mechanical properties by Q&P in commercial alloys: also the process step when the retained austenite is developing as well as occurring parallel formation of carbides may strongly influence this potential.

The world heritage object Nebra Sky Disc is one of the best investigated archaeological objects. The origin of the raw materials it is made of is well known. However, its manufacturing process was not completely clear. Investigations were made in order to clarify the steps of manufacturing from the initial casting to the finished disc using the latest metallographic techniques. Therefore, a small piece from the outer part of the disc was investigated and compared with a replica. Both were prepared regarding the metallographic procedure. Microstructural analysis was made by optical microscopy on a colour etched surface, EDS and electron backscatter diffraction. For the investigation of mechanical properties microhardness measurements were made. It could be found that the Nebra Sky Disc was manufactured from a flat cast followed by hot forging process. During the forging process the disc was heated and forged for approximately 10 times.