Neutron texture analysis on GEM at ISIS

doi:10.1016/j.physb.2006.06.091

Physica B: Condensed Matter

Volumes 385–386, Part 1, 15 November 2006, Pages 639-643

https://doi.org/10.1016/j.physb.2006.06.091 Get rights and content

Abstract

Texture analysis by time-of-flight neutron diffraction, carried out on a multidetector instrument, requires just a few sample orientations. Moreover, on a diffractometer like GEM at ISIS with sufficiently high detector coverage a quantitative bulk texture analysis can be performed even on a stationary sample in a matter of minutes. A ‘single-shot’, rapid texture measurement on a high-count-rate instrument can be of considerable benefit for studying materials at non-ambient conditions or for bulky samples that cannot be mounted on a goniometer. The capabilities of GEM for texture analysis are demonstrated with results on copper texture standards, which were studied to accompany diffraction analyses of archaeological objects.

Introduction

Neutron diffraction is a well-established tool in engineering and geological sciences for quantitative analysis of the crystallographic texture of a material, which is related to geological and mechanical deformation processes. Low absorption of neutrons is of considerable advantage for studying big, coarse-grained geological samples but also for testing intact and unique museum objects for which sampling is unacceptable. Texture is measured by recording diffraction patterns as a function of the scattering angle, either by (i) rotating the sample on a goniometer and/or by (ii) using a multi-detector surrounding the sample. The amount of texture information is roughly given by the product of the number of pole figures (h k l) times the number of sample orientations [1]. Hence, by using a polychromatic beam and with many detectors at fixed scattering angles, time-of-flight (TOF) neutron diffraction has some considerable advantages for texture analysis since significant portions of both reciprocal space and orientation space are simultaneously covered in one measurement. The capabilities and benefits of extracting the orientation distribution function (ODF) of a material from TOF data is well documented both from the experimental and the data treatment point of view. TOF texture analysis with a multidetector set-up was previously demonstrated at the pulsed source IBR-2, Russia [2] and at the pulsed spallation source LANSCE, USA [3]. Moreover, in the past few years Rietveld codes such as MAUD [4] and GSAS [5] have been developed to determine texture coefficients from TOF data. Texture measurements increasingly take advantage of this development in crystallography and Rietveld analysis, allowing texture information from complex low symmetry and polyphase materials to be extracted.

By increasing the detector coverage on a TOF diffractometer fewer sample rotations are required for quantitative texture analysis, as was demonstrated on HIPPO at LANCSE [3], [6] with typically 4–8 sample orientations and total collection times in the order of 20 min. Here we show that on GEM at ISIS, quantitative texture information can be obtained even faster from a single measurement without any sample rotations. Results on copper reference samples that were measured to calibrate the diffraction results of complex archaeological metal objects are presented to assess the texture analysis capabilities of GEM.

Section snippets

Experimental details

GEM is a high-count-rate materials diffractometer designed to study the structures of both crystalline and liquid and amorphous samples [7]. GEM is equipped with 6 detector banks, housing a total of about 7000 individual detector elements with banks 1 and 6 covering forward and backscattering angles, respectively (Fig. 1(a)). One detector element is typically about 5×200 mm² in size, corresponding to an angular coverage of about 0.2°×10° for a typical sample–detector distance at 90°. The total

Results and discussion

Fig. 2 shows reconstructed (1 1 1), (2 0 0) and (2 2 0) pole figures of the cold-rolled sample 1 for the three setting of Fig. 1(b)–(d) with data collection times of 2 min per orientation. The pole figures showing the typical hallmarks of a rolling texture are very similar for the three types of coverage models. Maximum multiples of a random distribution (m.r.d.) values and texture indices F² [1] are in reasonable agreement (Table 1). It can be concluded that the texture can be determined from a

Acknowledgements

Support by L. Lutterotti, University of Trento, Italy, with the MAUD program is gratefully acknowledged. We would like to thank H. Phiesel, Bonn University, Germany, for providing the reference samples.

References (7)

H.-R. Wenk et al.
Nucl. Instr. and Meth. A
(2003)
H.-R. Wenk et al.
Rep. Prog. Phys.
(2004)
K. Feldmann et al.
Textures Microstruct.
(1991)

There are more references available in the full text version of this article.

Cited by (50)

The use of time-of-flight neutron Bragg edge imaging to measure the residual strains in W/Cu dissimilar joints for fusion reactors
2024, Nuclear Materials and Energy
The European DEMOnstration power plant (EU DEMO) project is currently leading the research endeavours within the fusion field with the goal of developing a next generation fusion reactor. Given the challenging nature of the application, it is essential to establish methodologies that can provide convenient and reliable characterisation of the chosen materials within DEMO. In this paper, the recently developed Time-of-Flight Neutron Bragg Edge Imaging (TOF-NBEI) was used on Tungsten (W)/ Copper (Cu) dissimilar joints sample mock-ups of the cooling system design used in the critical divertor component with the goal of mapping the residual stresses across the sample. Residual strain mapping was performed on the W phase with considerable tensile residual strains identified close to the W-Cu interface. The large-grain microstructure of the Cu phase was analysed using the energy-resolved neutron radiographs. The results will be used as a basis for future TOF-NBEI experiments of tungsten monoblocks related to DEMO.
Application of a new method for accurate determination of α and β texture in Ti-6Al-4V from synchrotron diffraction intensities
2023, Materials Characterization
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.
Microstructural characterization through grain orientation mapping with Laue three-dimensional neutron diffraction tomography
2022, Materials Today Advances
Citation Excerpt :
The presence of twins is also verified by EBSD, as shown in Fig. S2 of the supplementary material. Given the results presented above, Laue 3DNDT is intended to complement and not replace traditional neutron diffraction methods for evaluation of crystallographic texture, which can be superior in terms of experimental time and statistical relevance [44–48]. Such methods have been widely used for texture assessment, not only ex-situ, but also in-situ during thermal treatments [49–51] or deformation tests [52].
For polycrystalline materials, key material properties, such as mechanical anisotropy or transformation behavior, and magnetic properties strongly depend on the crystallographic texture of the crystalline material. Assessment of texture is generally destructive and highly local. Only high energy X-ray diffraction at synchrotron sources and neutrons enable to study, non-destructively, the microstructure in the bulk of materials. Here, we report how progress in Laue three-dimensional neutron diffraction tomography enables to index the crystallographic orientation of several hundred grains and, thus, enables grain-resolved characterization of texture in the volume of centimeter-sized coarse-grained samples with statistical significance. To demonstrate the neutron technique for characterizing the crystallographic microstructure, we investigate a Fe-Ni-Mn austenitic alloy. A total number of 481 grains within a 1 cm³ of material is indexed and the results in assessing the crystallographic texture are compared with electron backscatter diffraction measurements. The short exposure times and non-destructive nature of the Laue three-dimensional neutron diffraction render it a novel promising method for corresponding characterization.
Mechanical properties and crystallographic texture of non-oriented electrical steel processed by repetitive bending under tension
2022, Materials Science and Engineering: A
Improving the magnetic properties of non-oriented electrical steel (NOES) through the optimization of crystallographic texture has been an on-going research activity for decades. However, using traditional rolling and annealing procedures, the obtained final textures were usually very similar, i.e., exhibiting the {111} (γ) and <110> (α) fibres, which were not the desired {001} texture (θ-fibre) for optimal magnetic quality. In the current work, a 1.8 wt% Si NOES was processed using a new sheet metal deformation method, i.e., repetitive bending under tension (R-BUT), also known as continuous bending under tension (C-BUT), to modify the texture of the electrical steel. The hot-rolled and annealed NOES plates were repeatedly bent and unbent when they were pulled under tension. The deformed plates were then heat treated at different temperatures for various times. Neutron diffraction and electron backscatter diffraction (EBSD) characterisation of the macro- and micro-textures proved that the R-BUT process significantly reduced the undesired {111} texture while promoting the {001} texture. The cube texture, which rarely formed after conventional rolling and annealing, was also seen in the R-BUT samples after annealing. It was shown that, the shear plastic deformation (induced by R-BUT) played a significant role in promoting the desired textures. In addition, the results indicated that the NOES processed by R-BUT could be deformed beyond its common formability limit, which may provide a method to address the poor workability challenge of high silicon electrical steels.
A new route for developing ultrafine-grained Al alloy strips using repetitive bending under tension
2021, Materials and Design
In this work, the mechanical behaviour and microstructure changes of AA-7075 alloy subjected to a repetitive-bending-under-tension (R-BUT) process were studied. In the R-BUT process, a metallic strip undergoes repeated localised bending and unbending. Load-displacement curves derived from R-BUT tested samples displayed a drastic increase in elongation to failure as compared to samples subjected to standard tensile tests. Additionally, the results confirmed that the force required to deform the R-BUT samples is much reduced as compared to the load required during simple tension. Finite element analysis confirmed that the sample subjected to the R-BUT process underwent intense shear deformation. Transmission-electron-microscopy (TEM) and electron-backscattered-diffraction (EBSD) analysis of the deformed matrix from the ND-RD plane (through-thickness) exhibited evidence for the formation of fine grains. TEM analysis confirmed that the fine grains formed were in the size range of 200–400 nm. Intense shear deformation experienced by the matrix led to shearing followed by spheroidization of precipitate particles. The influence of precipitate particles on the grain refinement process through Particle Stimulated Nucleation of fine grains in the matrix is also presented. EBSD analysis suggested that a Continuous Dynamic Recrystallisation process is the key mechanism behind the grain refinement in the sample during R-BUT processing.
Lattice strain development in an alpha titanium alloy studied using synchrotron and neutron diffraction
2021, Materials Science and Engineering: A
Neutron and high-energy X-ray diffraction methods have been used to investigate deformation mechanisms (slip and twinning activities) during uniaxial tensile tests of Grade 1 commercially pure titanium (Ti-α). These two diffraction techniques have provided valuable and complementary information. The predictions made by an Elasto-Plastic Self-Consistent (EPSC) model, taking into account grain reorientation and stress relaxation induced by twinning activity, have been compared with the experimental data. Results clearly demonstrate that there is a good agreement between simulations and diffraction measurements. The EPSC model enables accurate predictions of: (i) the lattice strains developed in variously oriented {hk.l} grain families within the bulk material, (ii) the grain reorientation induced by twinning activity and (iii) the macroscopic stress-strain response. Two different textured products were studied in order to evaluate the influence of texture on the mesoscopic and macroscopic responses of Ti-α alloy.

View all citing articles on Scopus

View full text