Abstract. Deformation twinning, martensitic phase transformation and mechanical properties of austenitic wt%Mn alloys with additions of aluminium and silicon have been investigated. Tensile tests were carried out at different strain rates and temperatures. The formation of twins, a'-and c-martensite during plastic deformation was analysed by optical microscopy, X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The stacking fault energy y h and the free energy AG"+E for the y +~ phase transformation were calculated using the regular solution model. It is known that additions of aluminium increase yfc, and therefore strongly suppress the y+c transformation while silicon decrease yf,, and sustains the y-E transformation. The y-+c phase transformation takes place in alloys with yk, 5 20 mllm2. The stacking fault energy of the Fe-25Mn-3Si-3A1 alloy was calculated as a function of temperature and related with microstructural changes of the strained sample at different temperatures. These steels with reduced density of about 7,3 g/cm-3 combine high tensile ductility up to 80 % at high strain rates with true tensile strength of about 1000 MPa. The excellent plasticity induced by twinning and additional phase transformation up to extreniely high strain rates of about E = lo3 s-' results in an extraordinary shock resistence and enables deep drawing and backward extrusion operations of parts with complex shapes and high production rates.

To reproduce focusing in virtual microscopy, it is necessary to construct 3-dimensional (3D) virtual slides composed of whole slide images with different focuses. As focusing is frequently used for the assessment of Helicobacter pylori colonization in diagnostic pathology, we prepared virtual 3D slides with up to 9 focus planes from 144 gastric biopsy specimens with or without H pylori gastritis. The biopsy specimens were diagnosed in a blinded manner by 3 pathologists according to the updated Sydney classification using conventional microscopy, virtual microscopy with a single focus plane, and virtual 3D microscopy with 5 and 9 focus planes enabling virtual focusing. Regarding the classification of H pylori, we found a positive correlation between the number of focus planes used in virtual microscopy and the number of correct diagnoses as determined by conventional microscopy. Concerning H pylori positivity, the specificity and sensitivity of virtual 3D microscopy using virtual slides with 9 focus planes achieved a minimum of 0.95 each, which was approximately the same as in conventional microscopy. We consider virtual 3D microscopy appropriate for primary diagnosis of H pylori gastritis and equivalent to conventional microscopy.

Advanced multiphase steels offer a great potential for bodies-inwhite through their combination of formability and achievable component strength levels. They are first choice for strength and crash-relevant parts of challenging geometry. The intensive development of high-strength multiphase steels by ThyssenKrupp has led to hot dip galvanizing concepts with an outstanding forming potential. Hot rolled, hot dip galvanized complex phase steels are currently produced in addition to cold rolled DP and RA steels.New continuously annealed grades with tensile strength levels of up to 1000 MPa in combination with sufficient ductility for applications mainly in the field of structural automobile elements make use of the classic advantages of microalloying as well as the principles of DP and TRIP steels. Further improvement of properties will be reached by the new class of high manganese alloyed steels.Keywords: high-strength steels, multiphase steels, high manganese steels, properties, body in white Fortschrittliche Multiphasen-Stähle eröffnen wegen der inzwischen erreichbaren Kombination aus Umformbarkeit und Bauteilfestigkeit ein enormes Potenzial für Rohkarosserien. Sie stellen eine erste Wahl dar, wenn es um Festigkeit und um Crashsicherheit geht und besondere Anforderungen an die Bauteilgeometrien gestellt werden.Bei ThyssenKrupp hat die Entwicklung hochfester MultiphasenStähle in Verbindung mit dem Feuerverzinken zur Realisierung von Blechhalbzeugen geführt, die hervorragend formbar sind. Es werden heute feuerverzinkte Komplexphasenstähle neben den bewähr-ten kaltgewalzten Dualphasen(DP) -und Retained Austenit(RA)-Stählen produziert.Die neuen kontinuierlich geglühten Stahlvarianten mit Festigkeiten bis zu 1000 MPa in Kombination mit der bei Strukturbauteilen im Automobilbau geforderten Duktilität nutzen sowohl die klassischen Vorteile des Mikrolegierens aus und dazu die Prinzipien, die man bei DP-und TRIP-Stählen anwendet. Eine weitere Verbesserung des Eigenschaftsprofils wird mit dem neuen Stahltypus hochmanganhaltiger Stähle erreicht.

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