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We report the results of the microstructural characterizations and micro-texture analysis of a lightweight austenitic steel deformed at high strain rate (1200 s) using a split Hopkinson pressure bar. Formation of adiabatic shear bands (ASB) and plastic deformation mechanisms within neighboring grains are investigated by high-resolution electron backscatter diffraction (HR-EBSD). HR-EBSD reveals formation of athermal ε-martensite and ά-martensite within the shear bands, resulting in the formation of a brittle intersection structure. Crack initiation and propagation is seen in intersection structure. The thermally induced ε-martensite follows Shoji-Nishiyama crystallographic orientation relationship with parent austenite phase, while ά-martensite shows Burgers relationship with ε-martensite. A detailed examination depicts the presence of deformation twins in grains adjacent to the ASB. Furthermore, strain-induced ε and ά martensite are formed in the neighboring grains of ASB. The micro-texture of martensite variants is discussed in ASB and in the neighboring grains. [ABSTRACT FROM AUTHOR]

Abstract: For semi solid metal (SSM) slurries, in addition to the morphology, size, distribution and percentage of the solid phase particles, the microstructure of individual solid particles is another important parameter to be considered. This is particularly an issue when SSM billets are prepared by continuous stirring of the melt to temperatures below liquidus, as in the case of electromagnetic stirring of Al–Si alloys. Microstructural evolution of the electromagnetically stirred Al–Si alloy is investigated by means of optical and electron microscopy. Electron backscatter diffraction (EBSD) analysis of the stirred and unstirred cast billets has shown stirring to generate local misorientation within individual solid particles. This is an indication of growing dendrites undergoing plastic deformation during the course of SSM slurry preparation. The formation of dislocations and their subsequent rearrangement into subgrain boundaries has been shown by EBSD analysis and TEM studies of thin foil specimens respectively. [Copyright &y& Elsevier]

In this study, we used a combination of X-ray diffraction and electron backscatter diffraction (EBSD) to track the evolution of both the microstructure and texture in samples of X70 pipeline steel subjected to cold-rolling up to 80% thickness reduction and subsequent annealing at 800 °C and 850 °C. Our investigation of the macro-texture, using an X-ray method, indicates that weak texture in the as-received-steel was changed from ζ-fiber to ɣ-fiber and Ɵ-fiber after cold rolling. EBSD reveals a local grain refinement as a result of the formation of a substructure with a low angle grain boundary within cold-rolled ferrite grains near the ɣ-fiber and Ɵ-fiber textures. Development of a later substructure depended on the orientation of deformed ferrite grains. We observed partial recrystallization within grains with ɣ-fiber texture and a grain size of about 1.5 ± 0.5 μm after cold rolling. Annealing at 800 °C for 90 s caused incomplete static recrystallization with an inhomogeneous bimodal structure. Recrystallized grains depicted both ɣ-fiber and Ɵ-fiber textures, identical to their deformation textures. We achieved a homogeneous equiaxied grain structure using a higher annealing temperature of 850 °C, for 300 s. [ABSTRACT FROM AUTHOR]

Abstract: The role of various finishing rolling operations on the texture and mechanical properties has been studied for API (American Petroleum Institute) X100 steel. It has been found that both the finish rolling start and end temperatures influence the final texture and thus, the mechanical properties and the anisotropy of these properties. High temperature finish rolling produces a very weak texture. This texture is a result of dynamic recrystallization, and associated with large grain size and inferior mechanical properties. A slightly delayed start of accelerated cooling led to the formation of large fraction of polygonal ferrite and increased the ductility at the expense of strength. Near-isothermal rolling in the range of 790–810°C produced the highest texture intensities of both the desired {332}〈113〉 and the undesired {113}〈110〉 components. The latter texture components as well as the {100}〈110〉 component, mitigated the positive effect of the {332}〈113〉 component. On the other hand, a relatively higher finish rolling start temperature (840°C) and a low finish rolling end temperature (700°C) suppressed the strength of the {113}〈110〉 and {100}〈110〉 components, while the {332}〈113〉 component apparently was sufficient for the reduction of the anisotropy of mechanical properties. Partial deformation of the quasi-polygonal ferrites also appeared to have contributed to increasing the strength of the investigated steel. [Copyright &y& Elsevier]