Within the Collaborative Research Center 799 novel composite materials which consist of a highly alloyed TRansformation-Induced Plasticity/Twinning-Induced Plasticity (TRIP/TWIP) CrMnNi cast steel matrix and a partially stabilized zirconium dioxide (Mg-PSZ) ceramic, referred to as TRIP-Matrix-Composites, are developed. [1] By applying an external load larger than the yield strength, the TRIP steel matrix shows a strain-induced phase transformation from metastable austenite to a 0 -martensite which leads to a concurrent increase of strength and ductility. By contrast, stress-induced formation of a 0 -martensite occurs at stresses below the yield strength, i.e., during elastic deformation. [2] The stress-induced transformation of the partially stabilized ZrO 2 from tetragonal phase to monoclinic modification can result in a further increase of the strength. Currently the interstitial-free austenitic CrMnNi cast stainless steels with TRIP/TWIP effect are in use. Representative alloys are 16Cr-7Mn-3Ni, 16Cr-7Mn-6Ni, and 16Cr-7Mn-9Ni. [3,4] These austenitic steel grades typically show low yield strengths of the order of 180-200 MPa. As a result of the low stress levels, only small fractions of the ceramic phase can transform to the monoclinic structure. In order to assist the phase transformation of the ceramic phase from tetragonal to monoclinic, the current steel research in the CRC 799 is focused on the increase of strength, especially the yield strength of the austenitic TRIP/TWIP CrMnNi cast steels by solid solution strengthening by nitrogen. Furthermore, the reduction of delta ferrite volume fractions, the adjustment of a pronounced TRIP/TWIP effect at operating temperatures and improved resistance against the intercrystalline corrosion by the addition of nitrogen is desired. In recent years, highly alloyed TRIP and TWIP steels have received much attention in both academia and industry because of their superior mechanical properties. [5][6][7]12] The high-manganese TWIP steels can be divided in the alloying systems FeMnC and CrMnC with additions of the main alloying elements such as N, Al, Si. In these steels g ! e transformation and deformation-induced twinning can appear in dependence of the SFE of the austenite. It is commonly believed that stacking fault energies below 18-20 mJ m À2 favor the g ! e phase transformation and higher values favor the twinning of austenite. [8][9][10] The longest known FeMnC steels are characterized by manganese contents between 15 and 30% and an austeniticThe effect of the manganese content (0-11%) on the transformation temperatures, the mechanical properties and microstructure development of five highly alloyed 14Cr-XMn-6Ni cast stainless steels with 0.1% nitrogen was studied. The examinations reveal that the M s , A s , and A f temperatures decrease with increasing manganese contents. As a result of low austenite stability, room temperature austenitic-martensitic as-cast microstructure was formed at manganese contents between 0 and 3%. At manganese levels of 6% and higher a fu...

The fabrication process of nonoriented electrical steels comprises: casting, hot rolling, cold rolling and final annealing. The developments of new technologies for fabrication hot band offers new possibilities. In this paper we will shortly describe the similarities and differences with respect to the evolution of microstructure (grain structure) and texture along the conventional processing route and thin strip casting. We will point out the most relevant features at the different processing steps, which are important for optimum texture and microstructure of the finally processed material. Thereby we will regard ferritic FeSi steels, where no homogenization of the microstructure appears due to the austenite -ferrite phase transformation.

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In this article, evolution of microstructure and texture in non‐oriented electrical steels along novel strip casting route and conventional route are comparatively investigated in detail. It demonstrates the similar and important role of the microstructure and texture prior to cold rolling to finally obtain desirable recrystallization microstructure and texture in both routes. In both routes, a high intensity of cube‐fiber texture and a low intensity of γ‐fiber texture can be acquired in hot strips by optimizing the hot rolling and thermal treatment parameters. Accordingly, after cold rolling and annealing, a lower intensity of γ‐fiber texture together with a higher intensity of cube‐fiber texture, which are favorable for high‐permeability materials, can be obtained in both routes. The desired large grain size in the finally annealed materials to obtain low magnetic losses may be gained by choosing appropriate annealing conditions after the first stage of recrystallization. The features of microstructure and texture are similar at comparable stages. The main differences in the regarded different processing routes are in the practical efforts. The detailed results and deeply corresponding discussion on how the microstructure and texture develop during cold rolling and annealing in differently processed samples will be given in the future work.

The corrosion behaviour of nitrided, carburised and nitrocarburised samples of the steels X2CrNiMo17‐12‐2 (AISI 316L) and X2CrNiMoN22‐5‐3 (UNS 31803) was tested with electrochemical methods. Generally the current density potential curves of the samples are highly sensitive on the chromium depletion of the matrix due to the precipitation of chromium nitrides at the grain boundaries. It was observed that in this case, especially in 0.05M sulphuric acid, the passive current density in the complete range of the current density potential curve increases considerably. A criterion derived for the beginning of the decomposition of the expanded austenite allows the determination of its stability in dependence on the treatment temperature and time. The expanded carbon austenite has a higher thermal stability compared to the expanded nitrogen austenite. By controlled sequential removal of the samples surfaces the corrosion behaviour into the depth of the surface layers was investigated. Das Korrosionsverhalten nitrierter, carburierter und nitrocarburierter Proben der Stähle X2CrNiMo17‐12‐2 (AISI 316L) und X2CrNiMoN22‐5‐3 (UNS 31803) wurde mit elektrochemischen Methoden untersucht. Die Stromdichte‐Potenzial‐Kurven reagierten sehr empfindlich auf eine Chromverarmung der Matrix durch die Ausscheidung von Chromnitriden an Korngrenzen. Es wurde beobachtet, dass sich besonders bei den in 0,05M Schwefelsäure aufgenommenen Stromdichte‐Potenzial‐Kurven die Passivstromdichte im gesamten Bereich deutlich erhöhte. Ein daraus abgeleitetes Kriterium für den beginnenden Zerfall des expandierten Austenites ermöglicht eine Beschreibung seiner Stabilität in Abhängigkeit von den Behandlungsbedingungen. Der expandierte Kohlenstoffaustenit besitzt eine höhere thermische Stabilität als der expandierte Stickstoffaustenit. Durch kontrollierte Schichtabträge wurde das Korrosionsverhalten der Randschicht mit wachsendem Oberflächenabstand untersucht.