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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 decreases. At all temperatures is dominant.

The effect of deformation temperature and strain rate (collectively described by the Zener-Hollomon parameter Z) on the deformation mechanism and texture formation of the metastable β-titanium alloy Ti5321 across the β-transus temperature during hot-compression was investigated by electron backscatter diffraction. In the β-phase field, it is found that the deformation behavior and texture formation varies depending on Z. With decreasing Z dynamic recovery and dynamic recrystallization become more and more important. The activation energy for steady state deformation is 240 kJ/mol and 370 kJ/mol in the β- and (α + β)-phase field, respectively. The texture developed is a double-fiber with < 100 > dominating at all deformation conditions. The fiber gets more prominent with increasing Z suggesting that it is mainly related to deformation. Flow softening behavior of Ti5321 is associated with dynamic globularization of the α-phase and promotion of β-grain formation by continuous dynamic recrystallization.

The microstructure and texture evolution of a metastable Ti-5Al-3V-3Mo-2Cr-2Zr-1Nb-1Fe alloy during bar-rolling and after various thermal treatments was investigated by high-energy synchrotron diffraction and electron backscatter diffraction. Bar-rolling is applied in the (α+β)-phase field in order to achieve a bi-modal (duplex) microstructure. The effect of dynamic recrystallized and recovered zones on texture of Ti5321was analyzed separately, as well as the texture of primary α-precipitates and secondary α-lamellae. The texture of the recovered zones is characterized by a cube component ({001}) plus α- and γ-fibre with dominant {100}, {112}, {111} components, while the texture of the recrystallized zones is a strong cube texture. After aging or recrystallization plus aging, this texture component remains, while it disappears after solution treatment. The primary α-precipitates have their c-axes perpendicular to the rolling direction and do not follow the Burgers orientation relationship. This texture characteristics remains after various thermal heat treatments. Secondary α-lamellae obey the Burgers orientation relationship. Moreover, a variant selection of secondary α-lamellae occurs. The mechanism of texture formation of the β-phase and the precipitation behavior of the α-phase is discussed. The hardness increase can be attributed to size, shape and volume fraction of the α-precipitates. Different combinations of primary α- and secondary α-precipitates make an increase in hardness of about 11%.

Aluminium sheets of high purity were produced by accumulative roll bonding (ARB) at room temperature. The microstructure of the sheets up to 16 ARB cycles was analyzed by scanning electron microscopy. In all sheets discontinuous dynamic recrystallization occurred leading to coarse grains. In general, the grain size decreases with increasing number of applied ARB cycles, but remains much larger than the theoretical layer thickness after 6 or more ARB cycles. It is shown for the first time, how the interfaces introduced by ARB have a significant effect on the elongated grain shape by a combined experimental-numerical-study: The resulting microstructure is qualitatively discussed with regard to defects introduced at the interfaces by the ARB process, while two-dimensional Potts model simulations yield very good qualitative agreements with the experiments and underpin the importance of the ARB interfaces as barriers for the motion of grain boundaries.

The change in microstructure during training of a Ni50Mn29Ga21 bicrystal was investigated by electron backscatter diffraction in a scanning electron microscope. The martensitic variants form macro and micro twins which are twin related with each other. The twin plane is of type. To achieve magnetic field induced strain in Ni-Mn-Ga alloys, a training process was applied. This process consists of successively compressing the sample along two axes. As a result the twinning stress is reduced and the twinning strain is maximized.

We have fabricated micro-/nano-pillars of a Zr-based metallic glass, Zr(50)Ti(16.5)Cu(15)Ni(18.5), with pillar tip diameters ranging from similar to 750 nm to similar to 110 nm. These pillars were mechanically tested quantitatively in-situ in a Transmission Electron Microscope (TEM). Due to a slight tapering of similar to 3, the deformation accommodated with shear bands is driven downwards from the top. However, the real time monitoring of shear bands evolution in-situ in TEM makes it possible to measure the effective load-bearing diameter, i.e., the diameter ahead of the most forefront shear band, which enables the precise measurement of yield strength of these pillars. Consequently, it turns out that the yield strength is essentially size independent and close to the bulk value. Statistical physics description of strength of small size metallic glasses is discussed, and it is concluded that Weibull Statistics is inappropriate in describing strength of metallic glasses at micro and nano length scales.

In order to quantify the plastic anisotropy of the ultrafine grained aluminium alloy AA6016 produced by accumulative roll-bonding (ARB) the Lankford parameter is measured by tensile testing as a function of the number of ARB cycles. The experimental results are compared with those from texture-based Taylor simulations. Increasing differences between experiment and theory at higher number of ARB cycles may be attributed to highly oriented microstructural features.

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The Hall effect is a powerful tool for investigating carrier type and density. For single-band materials, the Hall coefficient is traditionally expressed simply by , where e is the charge of the carrier, and n is the concentration. However, it is well known that in the critical region near a quantum phase transition, as it was demonstrated for cuprates and heavy fermions, the Hall coefficient exhibits strong temperature and doping dependencies, which can not be described by such a simple expression, and the interpretation of the Hall coefficient for Fe-based superconductors is also problematic. Here, we investigate thin films of Ba(Fe₁₋ₓCoₓ)₂As₂ with compressive and tensile in-plane strain in a wide range of Co doping. Such in-plane strain changes the band structure of the compounds, resulting in various shifts of the whole phase diagram as a function of Co doping. We show that the resultant phase diagrams for different strain states can be mapped onto a single phase diagram with the Hall number. This universal plot is attributed to the critical fluctuations in multiband systems near the antiferromagnetic transition, which may suggest a direct link between magnetic and superconducting properties in the BaFe₂As₂ system.

Titanium of commercial purity was deformed by equal channel angular pressing (ECAP) with back-pressure at 380 degrees C using 4 passes of route B-C. Billets of 120 min length were pressed at 0.4 min s(-1) through square channels (14 mm x 14 mm) intersecting sharply at an angle of 90 degrees. The global texture measurements of the starting and ECAP processed material were done by neutron diffraction. To investigate the texture inhomogencity after ECAP the local texture was measured with high-energy synchrotron radiation at different positions in the cross-section of the billet. The texture gradient with regard to intensity and orientation of the dominant texture component is characterized and discussed. Entnommen aus TEMA

Recovery and recrystallisation processes in polycrystalline metals are driven by the release of energy stored in defect structures chiefly resulting from dislocation creation, motion and interaction during plastic deformation. Some statistical models of texture change during recrystallisation employ the Taylor factor to quantify the distribution of this stored energy amongst orientations. While the Taylor factor is an instantaneous measure of the plastic power dissipation per orientation for a given strain mode, it is technically only valid as an estimate of stored energy if strain path and texture can be assumed constant. This motivates the search for alternatives to the Taylor factor which do not neglect the effects of changing strain path and evolving texture. In this paper a first step is made toward this goal by comparing the Taylor factor with a possible alternative, the accumulated slip per orientation, for a plane strain compression deformation of a bcc material. It is discovered that even for this idealised deformation there are specific orientations for which there is a consistent difference between the two parameters at various magnitudes of strain. It is concluded that these results lend support to the case for replacing the Taylor factor with a history based parameter in recrystallisation texture models. proceedings paper ispartof: pages:1-4 ispartof: IOP Conference Series: Materials Science and Engineering vol:82 issue:1 pages:1-4 ispartof: ICOTOM 17, International Conference on Textures of Materials location:Dresden, Germany date:24 Aug - 29 Aug 2014 status: published

Roping as a heterogeneous plastic deformation is generally attributed to the occurrence of the meso-scale clustering of grains with similar orientations. Large-scale electron backscattered diffraction (EBSD) orientation maps are customarily used to correlate the orientation topography with the roping profile. The most common way of investigating this phenomenon is to extract the predominant texture components and then to correlate them with the roping profile, since grains belong to different texture components lead to different plastic responses. Instead of using a microscopic representative volume element in the length scale of the grain size, the present work proposes a moving window mechanical model to use a representative volume element of the meso-scale, corresponding to a grain cluster, to simulate roping. For a tensile test in the transverse direction, a quantitative prediction of surface roping profile can be obtained. For an artificial EBSD orientation map, the proposed model can yield both roping wavelength and amplitude. ispartof: pages:012094- ispartof: ICOTOM 17, 17th International Conference on Textures of Materials vol:82 issue:1 pages:012094- ispartof: ICOTOM, International Conference on Textures of Materials location:Dresden, Germany date:24 Aug - 29 Aug 2014 status: published

An attempt was done to improve the quality of deformation texture predictions by statistical models through the introduction of "clusters" of N grains thus defining a third, intermediate length scale. The interaction between each cluster and the macroscopic length scale is of the Taylor type, whereas inside each cluster a VPSC scheme is used. Predictions of cold rolling deformation textures were quantitatively compared with experimental results for a steel alloy. The results are encouraging.

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© Published under licence by IOP Publishing Ltd. The effects of interstitial content and temperature on texture and substructure evolution of commercially pure titanium during the first pass of equal channel angular pressing were investigated. Different values of critical resolved shear stresses were proposed for different interstitial contents and processing temperatures. Simulation results show that texture was affected by both interstitial element and temperature. Also, in substructure simulation, the cell size was affected by interstitial content, while the fragment size was more dependent on temperature change. ispartof: pages:1-4 ispartof: IOP Conference Series: Materials Science and Engineering vol:82 issue:1 pages:1-4 ispartof: 17th International Conference on Textures of Materials (ICOTOM) location:Dresden, Germany date:24 Aug - 29 Aug 2014 status: published