ALBERT

Notes: The microstructure evolution in the deformation zone around second phase particles of IFsteel sheets subjected to tensile deformation has been investigated in order to correlate it to thedamage at microstructural scale. The experimental set-up consisted of a series of interrupted tensiletests which were carried out at different tensile deformations up to fracture. The microstructure ofthe deformed samples was investigated by EBSD analysis in which the EBSD scans were focusedon the areas containing Ti (C, N) particles of cubical shape. It was found that at tensile strains below25%, the ferrite matrix exhibited the evolution of slip bands inside specific grains depending ontheir crystallographic orientation although no special strain localization around the particles wasobserved. After 35% of tensile strain, the strain concentrates around the particles and particle-matrixdecohesion was observed. The lattice rotations of the matrix surrounding the particles as well as theselective deformation of the grains are analyzed and discussed

Notes: The distribution of the characteristic texture components between the ferrite grains of different size classes has been studied in a steel with 0.082%C, 1.54% Mn, 0.35% Si, 0.055%Nb and 0.078%V after different rolling schedules with a final rolling temperature above or below Ar3. Microstructures and textures were characterized by means of optical microscopy and orientation microscopy. A strong grain refining effect together with a bimodal grain size distribution was observed in the steel bothafter final rolling in the intercritical region or in the austenite region, close to the Ar3d temperature. The differences in grain size were interpreted on the basis of three potentially acting mechanisms: (i) transformation- induced recrystallization, (ii) increased mobility of specific grain boundaries and (iii) fast nucleation offerrite grains on specific sites of the parent austenite microstructure. The experimental data clearly favoured the third of these assumptions as the responsible mechanism for the observed bimodal grain size distributions

Notes: The shape memory behaviour of a Fe29Mn7Si5Cr based alloy has been investigated.Characterization of the martensitic transformation and the different structural constituents wasperformed using optical microscopy, X-ray diffraction (XRD) methods and electron backscatterdiffraction (EBSD). The transformation temperatures and the shape recovery were determined bydilatometry on prestrained samples

Notes: It is often assumed that the texture formation during solid state transformations in lowcarbon steels critically depends on the local crystallographic misorientation at the interface between transformed and not yet transformed material volume. In some cases, a theoretical crystallographic orientation relation can be presumed as a necessary prerequisite for the transformation to occur. Classical examples of such misorientation conditions in steel metallurgy are the orientation relations between parent and product grains of the allotropic phase transformation from austenite to ferrite (or martensite) or the hypothetical 〈110〉26.5º misorientation between growing nuclei and disappearing grains in a recrystallization process. One way to verify the validity of such misorientation conditions is to carry out an experiment inwhich the transformation is partially completed and then observe locally, at the transformation interface, whether or not the presumed crystallographic condition is complied with. Such an experiment will produce a large set of misorientation data. As each observed misorientation Dg is represented by a single point in the Rodrigues-Frank (RF) space, a distribution of discrete misorientation points is obtained. This distribution is compared with the reference misorientation Dgr, corresponding to a specific physical condition, by determining the number fraction dn of misorientations that are confined within a narrow misorientation volume element dw around thegiven reference misorientation Dgr. In order to evaluate whether or not the proposed misorientation condition is obeyed, the number fraction dn of the experimentally measured distribution must be compared with the number fractions dr obtained for a random misorientation distribution. The ratio dn/dr can be interpreted as the number intensity fi of the given reference misorientation Dgr. This method was applied on the observed local misorientations between the recrystallizing grains growing into the single crystal matrix of a Fe-2.8%Si alloy. It was found that the number intensity of the 〈110〉26.5º misorientation increased with a factor 10 when the misorientation distribution was evaluated before and after the growth stage. In another example the method was applied to the misorientations measured at the local interface between parent austenite and product martensite grains of a partially transformed Fe-28%Ni alloy. It could be established that the Nishiyama- Wasserman relations ({111}g//{110}a 〈112〉g//〈110〉a) prevail over the Kurdjumov-Sachs relations ({111}g//{110}a and 〈110〉g//〈111〉a) although a considerable scatter was observedaround either of the theoretical correspondences. A full parametric misorientation description was also applied to evaluate the relative grain boundary energies associated with a set of crystallographic misorientations observed near triple junctions in Fe-2%Si. In this instance it was found that the boundaries carrying a misorientation of the type 〈110〉w carry a lower interfacial energy than the 〈100〉 or 〈111〉 type boundaries

Notes: The toughness anisotropy in steel plates (0.08%C, 1.52%Mn, 0.3%Si, 0.055%Nb and 0.078%V) was studied in relation to the crystallographic texture and microstructural anisotropy of the material. The plates, with a ferrite –pearlite microstructure, were obtained by hot rolling in a laboratory reversible rolling mill to 66% reduction with the final rolling pass in the two-phase (g/a) domain followed by accelerated cooling to 570°C and subsequent slow cooling to room temperature (coiling simulation). Standard size Charpy samples with their long axis oriented at 0, 22.5, 45, 67.5 and 90° with respect to the rolling direction of the plate were tested at different temperatures varying from +20°C to –80°C. Microstructures and textures of the plates were studied by means of orientation scanning electron microscopy and XRD.A specific toughness anisotropy profile was observed which could not be correlated to the crystallographic texture of the plates, which all displayed very weak, almost random transformation type textures with a maximum intensity of approximately 2x random. Therefore, it was investigated whether the toughness anisotropy might be related to the microstructural anisotropy rather than to the crystallographic texture. The study of the grain size distribution in differently oriented sections together with the distribution of the pearlite zones in these sections revealed that the directional changes in the toughness could be successfully associated to these parameters.A significant increase in the absorbed impact energy from 140J to 270J, together with a remarkable decrease of the toughness anisotropy at room temperature, was observed after annealing the hot rolled samples at an intercritical temperature followed by an isothermal treatment in the low bainite region. The observed effect was explained by the replacement of the pearlite constituents by lower bainite in the grain boundary regions which produced a local strengthening of grain boundaries

Notes: The relationship between the misorientation of the austenite crystallites and the favouredsites for ferrite nucleation has been investigated. Ex-situ EBSD measurements were performed onan especially developed high purity ternary iron alloy with 20 wt.% Cr and 12 wt.% Ni with bothaustenite and ferrite present at room temperature to measure the misorientation between theaustenite crystallites. The experimental results are compared to the nucleation models of Clemm andFisher and Aaronson and co-workers

Notes: Electrical steels, in particular Fe-Si alloys, are used as magnetic flux carrier intransformers and motors because of their excellent magnetic properties. They owe these magneticproperties in part to the presence of specific texture components such as the Goss ({110} 〈001〉) orthe cube components ({001} 〈010〉), but also to the chemical composition which is optimum with6.5 wt. % Si. This high silicon content provides a stable BCC lattice structure to the alloy over theentire solid state domain, but also renders the material more brittle. This embrittlement, which isinduced by ordering phenomena, makes it impossible to produce the alloy in a conventional rollingprocess unless a specific thermomechanical route at high temperature is applied. In order toexamine the working behaviour of high Si electrical steels, a series of room temperature plane straincompression tests was carried out on a Fe-3%Si alloy in hot band condition. The samples werecompressed with a constant strain rate of 20 s-1 to a reduction of 10, 35 and 70% and subsequentlyannealed for different times at 800 and 900°C in an electrical furnace without protectingatmosphere.The hot rolled microstructure displayed an average grain size of 195 7m and the texture showedon the cube component ({001} 〈010〉) of maximum 5x random levels. After plane straincompression the samples developed the conventional α (〈110〉 // RD) / γ (〈111〉 // ND) fibretexture by plastic shear which was also accommodated, in part, by mechanical twinning. Withregard to the annealed material, it was observed that the recrystallisation started in grains with thehigher stored energy and within the shear bands. After a reduction of 70% the samples that wereannealed at 800°C for 4 hours displayed an average grain size of 27 7m and a relative maximum of4x random on the cube component. Also other less intense components such as the rotated cube({001} 〈110〉) and the Goss ({110} 〈001〉) were present in the annealing texture. The samples thatwere annealed at 900°C, after a reduction of 70%, were characterized by an average grain size of 367m and by the appearance of the {111} 〈121〉 γ fibre component with an intensity of 4.7

Notes: The present paper presents an overview of present and future tools which can be used bythe steel manufacturer in order to control the texture of the finished sheet product. The major solidstate-transformation processes (phase transformation, plastic deformation and recrystallisation)playing a role during thermo-mechanical processing will be addressed. The physical mechanismsthat give rise to the appearance of specific texture components will be discussed in detail. Inaddition to current state-of-the-art process technology the potential of innovative processes will bedescribed such as accumulative roll bonding (ARB). The present paper will also pay attention to theparticular role of surface textures as an additional degree of freedom allowing to control the sheettexture with the potential to enhance the {001} or {110} fibre textures for magnetic applications