The crystallographic texture development during processing of dual-phase Ti alloys like Ti-6Al-4V is of fundamental technological importance. However, measuring texture in both phases in these materials is a significant challenge because of the spatial inhomogeneity of the texture and low volume fraction of the minority β-phase at room temperature. Here we demonstrate how synchrotron X-ray diffraction can be used to overcome these difficulties and measure texture and texture variation in hot-rolled samples in a reproducible manner. The texture in hot-rolled Ti-64 was calculated from 2D synchrotron diffraction patterns obtained along different directions. The data was analysed using MAUD, which is based on Rietveld refinement of the diffracted intensities, and using a Fourier series based analysis method, that extracts intensities directly from the 2D diffraction patterns, and then uses the open-source software MTEX to fit an orientation distribution function (ODF). By comparing the results with faithful EBSD measurements, we show that the Fourier series method produces much more accurate texture measurements, especially for the minority β-phase. We also show that a minimum of 2, and preferably 3, different measurement orientations are needed to fully represent the texture. This implies that measurements of texture which rely on diffraction data from a single sample orientation, like in fast in-situ studies or spatially resolved measurements, can only provide qualitative information and must be interpreted with care.

This paper presents experimental results and finite element analysis of hot upsetting of titanium alloys Ti64 and Ti407 using a dilatometer in loading mode. All samples showed barrelling, as a consequence of an inhomogeneous temperature distribution and friction. The FE analysis is a full thermomechanical model of the test calibrated using multiple thermocouples. At each nominal temperature and strain rate, the true flow stress–strain response is inferred using the difference between the initially assumed constitutive response input to the FE analysis, $$\sigma =f\left(T,\dot{\varepsilon },\varepsilon \right)$$ , and the predicted response of the model. The analysis applies new procedures for: (1) modeling the thermal gradient; (2) finding the flow stress correction due to the inhomogeneity, using literature data as the input to the FE analysis; and (3) smoothing the constitutive data, fitting empirical $$\sigma =f\left(T,\dot{\varepsilon }\right)$$ surfaces at multiple discrete strains. The extracted true constitutive data confirm the moderate strain-softening behavior in Ti64 alloy, and the FE model predicts the distribution of local deformation conditions, for application in interpretation of microstructure and texture evolution. This highlights the difference between nominal and actual test conditions, showing that the discrepancy varies systematically with test conditions, with the central strain and strain rate being magnified significantly, by factors of order 2–3.

The factors controlling the evolution of abnormally coarse grain (ACG) structures during standard β annealing of titanium-6Al%-4V% (Ti64) hot-rolled plates, have been investigated in more detail than previously, using both ex-situ through-thickness large area, and in-situ EBSD micro-texture observation. Starting with a typical, through thickness, α+β deformation texture distribution that gives rise to ACGs at the plate mid-section, each stage of the annealing process has been sequentially characterised and phenomenologically linked to the spatial texture evolution that occurs during transient heating through the α→β phase transformation and the subsequent isothermal hold at the β-annealing temperature. It was found that during the ramp heating phase, the rotated cube texture component greatly expands from just below the β transus by broad front strain induced boundary migration (BF-SIBM), driven by a disparity in stored energy with neighbouring texture bands from the α and γ fibres. This subsequently sets up the necessary conditions for unstable coarsening of surviving grain clusters with predominately near α fibre orientations during the super-transus hold, in a process with similar characteristics to discontinuous recrystallisation. Humphreys’ mean field model of the stability of cellular microstructures, effectively explains the process by which these grain clusters, which have a lower misorientation range relative to the rotated cube component matrix, have a higher probability of entering a discontinuous growth regime, compared to other components from the α and γ fibres. Furthermore, the conditions that give rise to the development of ACG structures could be linked to the high strain rate and temperature experienced at the central mid-thickness of rolled plates.

The in-service properties and performance of dual-phase Zr and Ti alloys depend on their crystallographic texture, which develops during hot-working and is affected by interactions between the alpha and beta phases during deformation, annealing and phase transformation. Recent work on hot-rolled Zr-2.5Nb has shown that the texture of the two phases are related, with coupled strengthening of the alpha near {1120} <1010>, which produces strong 0002 pole intensities along the transverse direction, and beta with {001} <110> rotated cube, particularly when the relative volume fraction is around 50:50. To investigate the origin of this texture coupling, we studied a hot-rolled model Zr alloy with 7 wt.% Nb, in which the as-deformed alpha+beta microstructure is preserved on cooling. The alloy was hot-rolled to different reductions at 725 degrees C, which corresponds to a relative alpha:beta volume fraction of 30:70, where the characteristic textures are known to develop quickly at first and then weaken with further reduction. The rolled material was characterised using both 2D and 3D electron backscatter diffraction (EBSD). This analysis uncovered evidence that both recrystallization and phase transformation cause the disappearance of specific avariants during rolling, favouring the formation of "soft" primary agrains flattened in <1120> and elongated along <1010> during rolling, which in turn has an effect on surrounding beta orientations, promoting the stronger rotated cube component. At higher reductions, these elongated alpha-grains start to break up, as does the beta surrounding it, forming bands of characteristic coupled textures. These observations imply that non-plasticity effects should be included in models of texture evolution during processing of alpha+beta Zr and Ti alloys. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd.

In this work, a commercial cast magnesium alloy AZ31 was compressed at room and cryogenic temperatures (RT and CT) to study how the twins and dislocations affect the flow stress, plastic strain and strain hardening. Cryogenic deformation suppresses the dislocation activities to enable the effects of dislocation slip and twinning on plasticity to be separately interrogated. A quasi-in-situ Electron Backscatter Diffraction (EBSD) method was used to trace the evolution and distribution of twins and geometrically necessary dislocation (GND) density manifested as kernel average misorientation (KAM) in the same group of grains before and after plastic deformation, at RT and CT respectively. Compared to the RT deformation, higher flow stress, higher strain hardening rate and moderately reduced strain to failure were observed in the CT deformation. These interesting findings were rationalised by the subsequent EBSD analysis. It is found that the increased fraction of finer twins and twin-twin interactions rather than dislocation density leads to higher stress and higher strain hardening at CT. This suggests that the hardening effect induced by twin boundary and twin-twin interactions is considerably more effective than dislocation density hardening.

Compression dilatometer tests were used to study the hot deformation response of a zirconium (Zr)-2.5% niobium (Nb) alloy over the temperature range 650°C to 850°C and strain rates of 10−2.5 s−1 to 10+1 s−1. A high number of test conditions was used (72, with every test duplicated) in order to assess how differences in data processing influence the resulting relationships among flow stress, temperature, and strain rate. Particular attention was paid to processing maps, showing strain-rate sensitivity over the processing domain, commonly cited in the field and widely used as a basis to determine optimum processing conditions. Significant variations in these maps were found to depend on the number of data points included and the fitting procedure used to smooth the data. A finite element model of the test demonstrates the order of the corrections that can be required to the flow stress and the consequent processing maps due to friction at the platen-workpiece interface and nonuniform temperature and deformation in the test piece. Changes in crystallographic texture, measured using electron-backscatter diffraction, illustrate the effect of temperature, strain, and strain rate on the deformation, phase transformation, and recrystallization mechanisms. A significant spread in response arises as a result of variation in microtexture among samples and the tendency for flow to localize, giving rise to scatter in the measurements and generating artifacts in the processing map. Although the processing map methodology is strongly affected by experimental uncertainty, a detailed analysis of the final microstructures in the test samples shows similar features to those produced during industrial-scale processing, providing insight into the deformation mechanisms in dual-phase Zr-Nb alloys.

An improved understanding of the phenomenon of dynamic precipitation is important to accurately model and simulate many industrial manufacturing processes with high strength Al-alloys. Dynamic ageing in 7xxx Al-alloys can occur as a result of both the strain and heat. Small angle X-ray scattering (SAXS) is an advanced technique that allows the precipitation processes to be studied in situ, but to date this has only been possible at lower than industrially relevant strain rates (e.g. < 10−3). In this contribution, we demonstrate the potential of in-situ SAXS studies of metallic alloys at higher strain rates (10−2) than previously, using a high energy synchrotron X-ray. The time resolved SAXS information has been used to evaluate dynamic precipitate evolution models and has demonstrated that at high strain rates a new regime must be considered which includes the more significant effect of vacancy annihilation, leading to a clear strain rate, rather than just strain, kinetic dependence.

Additive Manufacture (AM) of Ti–6Al–4V frequently leads to undesirable, coarse, columnar β-grain structures with a strong <100> fibre texture. In Wire-Arc AM (WAAM), it has been found that the application of a low plastic strain, by methods such as inter-pass rolling, can disrupt β columnar growth and produce a refined, equiaxed grain structure that is more randomly orientated. The origin of this desirable effect has been investigated by thermo-mechanical simulation, direct in-situ EBSD observation, as well as by real-time synchrotron X-ray diffraction (SXRD) during rapid heating. These complementary approaches have shown that, when starting with a WAAM microstructure, the grain refinement process produces a unique micro-texture represented by a four-pole motif symmetrically centred on the parent grain {100} orientations. These new β-grain orientations can be reproduced by a double {112}<111> twinning operation, which produces 12 new, unique, β-orientation variants. High-resolution orientation-mapping techniques and in-situ SXRD heating simulations suggest that the prior β does not twin during deformation, but rather the grain refinement and related texture may be caused by annealing twinning during β re-growth on rapid re-heating of the deformed AM microstructure. Although this is the first time such a unique texture has been observed in a deformed and β annealed Ti–6Al–4V material, it was only found to dominate under the unusual conditions that occur in AM of rapid heating – a fine, lightly deformed α transformation microstructure, with a very coarse starting β-grain structure.

The evolution of peak profiles in synchrotron X-ray diffraction (SXRD) data can tell us how the

The microstructure of Ti-64 strongly affects the forming and in-service behaviour of aerospace components. The development of microstructure, including crystallographic texture, during thermomechanical processing involves changes caused by deformation, annealing and phase transformation. Recently, it has been reported that deformation and transformation occur concurrently, in a dynamic α → β transformation process, driven by the net flow softening it produces. Here, we present the results of an in-situ synchrotron diffraction experiment that aimed to detect and measure the extent of dynamic phase transformation during hot deformation and its contribution to the crystallographic texture of the alloy. Forged Ti-64 samples were deformed in uniaxial tension at 950°C and a strain rate of about 0.02 s-1, using an electro-thermal mechanical tester (ETMT) mounted on the I12: JEEP beamline at Diamond Light Source. By using a high energy 89 keV synchrotron X-ray beam and a fast acquisition rate (10 Hz) we were able to measure, during deformation, the internal elastic lattice strains in the two phases, the crystallographic texture of both phases and the α → β phase fraction. The results show, for the first time, direct evidence of dynamic transformation during isothermal hot deformation.

The properties and performance of Zr-2.5 Nb alloys are strongly influenced by their crystallographic texture. As in similar Ti alloys, the texture evolution during hot-processing depends on the complex interactions between the alpha and beta phases and involves deformation, annealing and phase transformation. Although the effect of temperature and deformation has been studied for extruded tube in this alloy, there is no data for texture development during rolling. There is some rolling data for Ti-64 (Ti-6Al-4V), but it is usually for just one of the phases and for a limited set of temperatures. We carried out hot-rolling trials from 700 degrees C-900 degrees C to reductions of 50%, 75% and 87.5% and found that the texture in both phases strengthens sharply before the beta-transus and when both phases are present in similar amounts. At this point, the texture in alpha is a strong 0002 parallel to TD and the texture in beta a strong {001}< 110 > rotated cube component. The results suggest there might be a synergistic effect between the two components, which includes dynamic phase transformation. The texture evolution towards stable alpha {11 (2) over bar0}< 10 (1) over bar0 > or {11 (2) over bar1}< 10 (1) over bar0 > crystallographic components and their final intensity depend on the starting texture. Texture was measured using electron-backscatter diffraction (EBSD) over large areas, with a beta reconstruction software used to determine the high temperature beta orientations. The texture development in Zr-2.5Nb appears similar to that reported for rolled Ti-64 at temperatures with equivalent phase fractions, although it is difficult to compare the two because of the lack of a titanium dataset as detailed as the one presented here. (C) 2019 The Authors. Published by Elsevier B.V.

The texture evolution during high-temperature rolling (800 degrees C) of two model zirconium-niobium alloys was studied using electron backscatter diffraction. The aim was to decouple the relative importance of deformation and phase transformation on the final texture in an effort to elucidate the origin of the strong a-transverse basal texture commonly found in the hot-rolled product. The analysis uses a reconstruction software based on the Burgers relation to reconstruct the high-temperature beta orientations, with the indexed a as input. In the low niobium content alloy, the texture evolution of the {11 (2) over bar0} < 10<(1)over bar>0 > component was consistent with deformation in both alpha and beta phases, along with a variant selection mechanism that occurred during the beta ->alpha phase transformation. Variant selection was observed to depend on the orientation of the deformed prior beta grains. In the high niobium content alloy, a lower alpha volume fraction during hot rolling gave rise to different beta textures and promoted the formation of a Goss component. This contributed to the {11 (2) over bar0} < 10<(1)over bar>0 > component upon cooling, with variant selection enhanced by anisotropic grain breakup.

Dual-phase alpha plus beta Zr-Nb alloys have a higher strength and fracture toughness than single-phase alpha alloys and develop different crystallographic orientations (textures) during thermo-mechanical processing. The textures developed at manufacture are particularly important in determining the life-limiting in-reactor behaviour of nuclear components. Dual-phase Zr alloys tend to form a strong transverse (TD) texture of the basal pole, the origin of which is poorly understood and cannot be predicted by crystal plasticity texture evolution models. This is because the microstructure and texture evolution of these dual-phase alloys arises from complex interactions between the alpha (hexagonal-close-packed, hcp) and beta (body-centred-cubic, bcc) phases, during both deformation and phase transformation. The work presented here is an investigation of the texture evolution during high temperature rolling of an industrially used Zr-2.5Nb alloy, along with the hot-rolling and uniaxial compression of two model dual-phase Zr-Nb alloys (Zircaloy-4 with 2.5 wt.% Nb and Zircaloy-4 with 7 wt.% Nb). The aim was to determine the relative roles of plastic strain partitioning between phases, the activity of the different deformation modes and phase transformation on the final texture. The effect of temperature (700C to 825C), reduction ratio (50% to 87.5%) and strain rate, along with the influence of starting texture, was characterised using time-of-flight (TOF) neutron diffraction and EBSD techniques. The alpha transverse texture component, with prismatic alignment {11-20} , strengthens with greater rolling reduction at the higher temperatures, accompanied by a weakening of basal part orientations with 0002 in ND. Software reconstruction of EBSD orientation maps, using the Burgers relationship, shows how the strength of the transverse texture component varies across the material depending on the orientation of large prior-beta grains. A more detailed characterisation of the high temperature deformation and phase transformation behaviour was made on a hot-rolled Zircaloy-4 with 7 wt.% Nb alloy. Since a greater proportion of metastable beta-Zr is retained to room temperature, a snapshot of the material before beta to alpha phase transformation can be captured, distinguishing high temperature primary alpha grains from the nucleation and growth of secondary alpha variants. By analysing these structures in 3D, using a plasma focused ion beam (PFIB) and taking sequential EBSD slices, it was found that the degree of breakup is affected by the distribution of primary alpha laths within each beta-grain. Further analysis shows that the orientation of the primary alpha influences the breakup behaviour of the beta-grains. Softer alpha orientations, with 0002 in TD, are favoured through a slip compatibility with the beta-matrix. Harder alpha grain orientations develop a much higher misorientation, with a greater stored energy to undergo a dynamic transformation, during deformation. These findings suggest new ways in which the current models can be developed, to enable the successful prediction of hot-rolling textures in these alloys.