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Microstructural characterization of deformation-induced martensite in its early stage of formation has been performed in an ultrafine-grained (UFG) medium Mn advanced high strength steel (AHSS). By using field emission scanning electron microscope (FESEM) and electron backscattered diffraction (EBSD), the nucleation site of deformation-induced martensite has been studied. Grain sizes, Schmid factors and aspect ratios of the parent austenite grains of deformation-induced martensite were measured in order to know their influence on the formation of deformation-induced martensite. Orientation relationship between deformation-induced martensite and its parent austenite has also been analyzed. Discussion on the effect of microstructural parameters on the formation of deformation-induced martensite in AHSS is given. [ABSTRACT FROM AUTHOR]

Abstract: The effects of Ti, Ti–Mo, and Ti–Nb microalloy additions on the precipitation strengthening in three experimental high-strength low-alloy steels have been investigated. The objective of this work was to study the carbide precipitation under the conditions of continuous cooling and interrupted cooling. It was found that titanium molybdenum complex carbide, (Ti, Mo)C, can strongly maintain nanometer-scaled sizes and has the largest contribution to the hardness as compared to titanium carbide, TiC, and titanium niobium complex carbide, (Ti, Nb)C. The result emphasizes that (Ti, Mo)C particles possess an excellent behavior of thermal stability. [Copyright &y& Elsevier]

Abstract: The coated zinc layer on the dual-phase steel can possess excellent anti-corrosion properties, and the continuous hot-dip process for the dual-phase steel is well known as galvannealed treatment. Since the coated layer is very thin, it is very difficult to acquire a thin foil for transmission electron microscopy by the traditional twin-jet method. The focused ion beam method was used in the present study to obtain high-quality specimens for investiging the details of the microstructure in the coated layer. It was found that a fully microalloying layer exists between the zinc layer and iron matrix. The zinc-rich phases ζ and δ can be observed in the coated layer. However, the Γ1 and Γ2 phases could not be detected in the present study, although they could be expected in parts of lower zinc content in the coated layer. [Copyright &y& Elsevier]