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Abstract: The evolution of microstructure and texture of a nanocrystalline Pd–10at.% Au alloy (initial grain size 16nm) subjected to severe plastic deformation by high-pressure torsion (HPT) at room temperature is investigated by X-ray line profile analysis and X-ray microdiffraction, respectively. In addition, changes in the microhardness are measured and the texture is modeled. During HPT the microstructure changes: the crystallite size goes over the maximum, the dislocation density goes through a minimum and the density of stacking faults decreases at/up to a shear strain of ∼1, corresponding to a grain size of 20nm. Starting with a random texture, typical brass-type shear components develop at a shear strain above ∼1. The microhardness with decreasing crystallite size goes over a maximum at ∼20nm. The correlated changes in microstructure, texture and strength strongly suggest the transition from a dislocation slip to a grain boundary sliding (GBS)-dominated deformation mechanism. The unexpected brass-type texture and its deviation from the ideal position can be simulated with the Taylor model assuming dominant partial dislocation slip and a certain contribution of GBS, respectively. Taken together, the results of many techniques applied to the same material, in particular those of the texture investigations, provide a more comprehensive and consistent picture of nanoplasticity than reported before for face-centered cubic metals. [Copyright &y& Elsevier]

Using synchrotron radiation, a comparison is made between torsion textures formed in nanocrystalline (nc) and coarse-grained (cg) samples of the Pd-10at.% Au alloy after identical shear strains. Intensities of characteristic components of shear texture are several times stronger in the cg sample than those in the nc one. This is regarded as evidence of increased activity of grain boundary-mediated deformation in the nc sample. Dislocation slip and twinning do not significantly contribute to the plasticity of the nc alloy. [Copyright &y& Elsevier]

Local texture and microstructure was investigated to study the deformation mechanisms during equal channel angular extrusion of a high purity nickel single crystal of initial cube orientation. A detailed texture and microstructure analysis by various diffraction techniques revealed the complexity of the deformation patterns in different locations of the billet. A modeling approach, taking into account slip system activity, was used to interpret the development of this heterogeneous deformation. [ABSTRACT FROM AUTHOR]

The texture in a polycrystalline Ni50Mn29Ga21 magnetic shape-memory alloy deformed by high-pressure torsion (HPT) at 1173K was investigated with high-energy synchrotron radiation. HPT changed the extrusion texture to a predominant slightly rotated cube {001} 〈100〉 and a weak F {110}〈100〉 component. During HPT the grain structure coarsened. Phase transformations during cooling from the deformation temperature led to coarse and fine sets of martensitic twin variants. The results are discussed with respect to deformation mode, grain growth and phase transformations. [Copyright &y& Elsevier]

Abstract: The texture of a cube-oriented Ni single crystal after one-pass equal channel angular pressing (ECAP) was measured globally and locally by neutron and synchrotron radiation, respectively. The texture is characterized by a TD rotated cube, a split C component and a partial B fiber. These components are heterogeneously distributed in the ECAP billet. Due to friction at the die walls, the rotated cube is mainly observed in the top and bottom parts of the billet, the split C dominates in the central part. The experimental results with respect to component intensity, position from ideal orientation and asymmetry of component splitting are compared with texture simulations taking into account grain fragmentation. Conclusions concerning polycrystal deformation are drawn. [Copyright &y& Elsevier]

Abstract: Aluminium with 5N purity were deformed at room temperature by equal channel angular pressing following Route A up to three passes. The microstructure and the crystallographic texture were investigated by orientation imaging microscopy and electron backscatter diffraction, respectively. The microstructure showed complete recrystallization after the first ECAP pass onwards. The grain size decreased slightly with increasing number of passes. The corresponding texture consisted of an oblique cube component. The oblate grains and the cube texture were rotated anticlockwise about the transverse direction. The inclination of grains with respect to the direction of ECAP was dependent on the distance from the top of the billet and changed from pass to pass. The mechanism of formation of the microstructure and texture is discussed in the light of the physical phenomena involved. [Copyright &y& Elsevier]

<1 0 0> and <1 1 0> oriented NiAl single crystals have been extruded at 1000 °C through a round die. The crystals subdivide into two types of deformation bands producing fibre texture components parallel and normal to the extrusion axis. These rotations as well as shape changes under partially constrained deformation conditions yield informations on the slip system activity. The relevance of deformation banding on texture formation in polycrystals is discussed. [Copyright &y& Elsevier]

Compression of NiAl polycrystals was carried out at room temperature under atmospheric as well as 0.4 GPa confining pressure at constant strain rate. The stress–strain curves show that the strength as well as the work-hardening rate is generally higher when deformed under hydrostatic pressure. Moreover, there is a strong plastic anisotropy, that is, samples having a 〈100〉 crystallographic preferred orientation parallel to the compression axis are much harder than those having 〈110〉 and 〈111〉. Similarly, the frequency of microcracking shows the same tendency. It seems that the microcracks in the samples deformed under confining pressure mainly result from internal stresses released after unloading. The strength of the differently textured samples at elevated strains correlates with the Taylor energy calculated. These calculations also explain for certain textures the deviation from a homogeneous shape change during compression towards plane–strain deformation. The textural changes produced by deformation are simulated with the Taylor model. [Copyright &y& Elsevier]

Abstract: To produce molybdenum sheets or ribbons the metal has to be thermomechanically processed leading to characteristic deformation and recrystallization textures depending on the deformation and/or annealing conditions. The so produced textures have an impact on certain properties of the metal. The present work concentrates on the influence of different rolling processes and the last step of heat treatment on microstructure, texture and the mechanical properties of molybdenum sheets. Usually, unidirectional rolling leads to a strengthening of the main texture component, which for molybdenum is a weak α-fibre with a maximum at the rotated cube component {100} <110>. This component leads to a strong anisotropy of the mechanical properties in the sheet plane. Cross rolling steps during the thermomechanical process increase the rotated cube component. To decrease the intensity of the rotated cube component and simultaneously increase the intensity of the γ-fibre, specific annealing stages of the final heat treatment were tested. The texture development during these annealing stages is discussed with regard to microstructural changes. The strong differences in the textures measured are reflected in the plastic anisotropy characterized by the Lankford parameters. The Taylor–Bishop–Hill theory is used to qualitatively explain the plastic anisotropy. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure, texture and mechanical properties of molybdenum sheets produced by different rolling processes were investigated by orientation imaging in the scanning electron microscope, X-ray diffraction and tensile tests, respectively. For comparable recrystallization degree of the sheets investigated, straight rolling with low reduction ratio produces α-fiber textures with a maximum at {100} 〈110〉. At higher rolling degrees the maximum shifts to {112} 〈110〉. Cross rolling increases the rotated cube component {100} 〈110〉. The strong differences in the texture measured are reflected in the plastic anisotropy characterized by differences in the yield stress and Lankford parameter which were measured along directions in the rolling plane at angles of 0°, 45° and 90° with the rolling direction. The Taylor–Bishop–Hill theory is used successfully to qualitatively explain the plastic anisotropy. [Copyright &y& Elsevier]

A flat specimen of sub-microcrystalline nickel was tensile tested at 4K until fracture occurred and subsequently investigated by electron backscatter diffraction in a high resolution scanning electron microscope in order to deduce the local texture in the near crack area. Thus, two sets of intersecting fine slip markings observed on the surface (under ±55° with respect to the tensile axis) could be explained as a result of localized simple shear in the bulk material underneath the slip markings. The overall amount of shear in the region near the crack was estimated to be 1.25 based on texture simulations using the viscoplastic self-consistent polycrystal model. [ABSTRACT FROM AUTHOR]

A flat specimen of sub-microcrystalline nickel was tensile tested at 4K until fracture occurred and subsequently investigated by electron backscatter diffraction in a high resolution scanning electron microscope in order to deduce the local texture in the near crack area. Thus, two sets of intersecting fine slip markings observed on the surface (under ±55° with respect to the tensile axis) could be explained as a result of localized simple shear in the bulk material underneath the slip markings. The overall amount of shear in the region near the crack was estimated to be 1.25 based on texture simulations using the viscoplastic self-consistent polycrystal model. [ABSTRACT FROM AUTHOR]

Abstract: Austenitic–ferritic duplex stainless steels are widely used for applications, where both excellent strength and high corrosion resistance are required. In the current study, high cycle fatigue experiments were performed on the austenitic–ferritic duplex stainless steel 1.4462 in order to investigate short crack initiation and propagation. It is shown that the most frequent crack initiation sites are grain boundaries between ferritic grains followed by slip bands in austenite and phase boundaries. Taking into account the elastic anisotropy of the austenitic phase, the surprisingly high fraction of cracks formed along slip bands in austenite can be explained with the texture and microstructure of the material. Analyzing the correlation between crack propagation rate and crack length, it is found that in both phases, the transition crack length between the regimes of microstructurally and mechanically short cracks correlates with the mean grain elongation under the average angle between crack path and loading axis. Additionally, the dependence of the crack propagation rate on the distance between crack tip and opposing grain or phase boundary, i.e. the barrier effect of these boundaries for short crack propagation, could be measured. The results obtained expand the knowledge about short crack behavior in the investigated material, which is a key parameter for the lifetime in the high cycle fatigue regime. [Copyright &y& Elsevier]

Abstract: The plastic anisotropy of ultrafine grained aluminium alloys AA1050 and AA6016 produced by accumulative roll bonding (ARB) has been investigated by tensile deformation via the Lankford parameter. The average normal and planar anisotropies slightly increase (from 0.6 to 0.9) and decrease (from 0.6 to −0.7) as a function of ARB cycles, respectively. The global textures measured by neutron diffraction are used to simulate the Lankford and anisotropy parameters of the plates after 0, 2, 4, 6 and 8 ARB cycles with the help of the viscoplastic polycrystal self-consistent model. Simulation results are compared with those from experiment and discussed with regard to texture, strain rate sensitivity, grain shape and slip system activity. [Copyright &y& Elsevier]

An investigation of cross-section deformation heterogeneities resulting from equal channel angular extrusion (ECAE) of a cube-oriented nickel single crystal – extruded through a squared section die – has been carried out. It is demonstrated that, even for a given initial single crystal orientation, strong differences in crystal orientation evolution and associated deformation patterns can develop locally. In particular, a significant heterogeneity prevailing along the transverse direction of the billet is reported for the first time. [Copyright &y& Elsevier]

Abstract: A two-phase lamellar and globular TiAl-based alloy (Ti–45Al–4(Cr, Nb, Ta, B)) with different textures has been deformed in torsion in a Paterson-type rock deformation machine at a temperature of 1173K under 400MPa argon confining pressure. The shear stress–shear strain curves with increasing shear strain show a decrease or increase of shear stress in the lamellar and globular case, respectively, to a common steady state value. Activation analysis at high strains yields stress exponents of about 1.8 and an activation energy of 3.29eV. With increasing shear strain the lamellar structure breaks down and a two-phase fine-grained globular structure develops by recrystallization with a grain size in the order of 2μm. The weak initial fibre textures at high strains are randomized. The mechanical, microstructural and textural features indicate a transition from dislocation creep to superplastic flow. [Copyright &y& Elsevier]

The microstructure and texture development of the metastable β ‑titanium alloy Ti5321 during hot-compression were investigated by electron backscatter diffraction. Above the β -transus temperature, deformation is accompanied by continuous dynamic recrystallization leading to immediate steady state flow. The deformation below the β -transus temperature is significantly affected by α -precipitation. Dynamic globularization of the α -lamellae leads to flow softening. During hot-compression, parallel to the compression axis a 〈100〉 〈111〉 double fiber texture develops. With increasing temperature the intensity of 〈100〉 increases, while that of <111> decreases. At all temperatures <100> is dominant. • Strain affects the types of dynamic recrystallization (DRX) during hot-compression. • DRX and plastic deformation affect <100>, <111> fiber texture formation. • Dynamic globularization of α-phase affects DRX, thus affects flow softening. [ABSTRACT FROM AUTHOR]

Equal channel angular pressing was carried out on Al–Mg alloys to study the effect of Mg addition on the microstructure, texture and strength after severe plastic deformation by 8 passes of equal channel angular pressing (ECAP) through route B c. The increase in Mg content enhanced the propensity of continuous dynamic recrystallization and simultaneously decreased the average grain size of the alloy. The microstructure and local texture was heterogeneous across the billet thickness for all the samples, irrespective of composition. All the samples showed a shear-type bulk texture generally observed in face-centred cubic metals with strong B E /‾B E components. The weakening of the texture with increase in Mg content is attributed to the substructure evolution during the ECAP process. The grain size and dislocation density have been determined by X-ray diffraction line profile analysis. The experimentally determined yield strength of the ultrafine grained samples can be explained by a combination of solid solution, dislocation and grain size strengthening, the latter being predominant. [ABSTRACT FROM AUTHOR]