Multi-scale characterisation of the 3D microstructure of a thermally-shocked bulk metallic glass matrix composite

Bulk metallic glass matrix composites (BMGMCs) are a new class of metal alloys which have significantly increased ductility and impact toughness, resulting from the ductile crystalline phases distributed uniformly within the amorphous matrix. However, the 3D structures and their morphologies of such composite at nano and micrometre scale have never been reported before. We have used high density electric currents to thermally shock a Zr-Ti based BMGMC to different temperatures, and used X-ray microtomography, FIB-SEM nanotomography and neutron diffraction to reveal the morphologies, compositions, volume fractions and thermal stabilities of the nano and microstructures. Understanding of these is essential for optimizing the design of BMGMCs and developing viable manufacturing methods

Energy-resolved neutron imaging for reconstruction of strain introduced by cold working

Energy-resolved neutron transmission imaging is used to reconstruct maps of residual strains in drilled and cold-expanded holes in 5-mm and 6.4-mm-thick aluminum plates. The possibility of measuring the positions of Bragg edges in the transmission spectrum in each 55 × 55 µm2 pixel is utilized in the reconstruction of the strain distribution within the entire imaged area of the sample, all from a single measurement. Although the reconstructed strain is averaged through the sample thickness, this technique reveals strain asymmetries within the sample and thus provides information complementary to other well-established non-destructive testing methods

Relaxor-to-ferroelectric crossover and disruption of polar order in "empty" tetragonal tungsten bronzes

JG would like to thank the EPSRC for provision of a studentship via the doctoral training grant (EP/K503162/1). The research data (and/or materials) supporting this publication can be accessed at [http://dx.doi.org/10.17630/a7a9bc13-b5cb-485d-914a-923832f25190]Combined temperature-dependent structural and electrical characterization of a series of “empty” ferroelectric tetragonal tungsten bronzes (TTBs) of composition Ba4(La1- xNdx)0.67□1.33Nb10O30 are reported. The La-material exhibits a temperature dependent crossover from relaxor-ferroelectric to polar (but non-ferroelectric) to linear dielectric behavior. The loss of ferroelectric switching in the polar, non-ferroelectric phase is accompanied by disorder associated with structural relaxation due the significant vacancy concentration at the A1-perovskite-like site. In this disordered regime, large polarization can be re-established with application of sufficient electric field, however relaxation back into the disordered phase occurs on removal of the field as indicated by the loss of remenant polarization. The field against which “backswitching” (depolarization) occurs increases with temperature indicating increasing stability of the disordered regime. The disordered phase can be de-stabilized by substituting Nd for La at the A1-site and which reintroduces “normal” ferroelectric behavior.PostprintPeer reviewe

Thermal evolution of the crystal structure of the orthorhombic perovskite LaFeO3

CALD and CMK were supported by EPSRC DTA studentships (EP/L505079/1).The thermal evolution of the crystal structure of the prototypical orthorhombic perovskite LaFeO3 has been studied in detail by powder neutron diffraction in the temperature range 25<T<1285 K. A conventional bond length/bond angle analysis, combined with an analysis in terms of symmetry-adapted modes, allows key aspects of the thermal behavior to be understood. In particular, the largest-amplitude symmetry modes (viz. in-phase and out-of-phase octahedral tilts, and A-site cation displacements) are shown to display relatively ‘normal’ behavior, increasing with decreasing temperature, which contrasts with the anomalous behavior previously shown by the derivative Bi0.5La0.5FeO3. However, an unexpected behavior is seen in the nature of the intra-octahedral distortion, which is used to rationalize the unique occurrence of a temperature dependent crossover of the a and c unit cell metrics in this compound.PostprintPeer reviewe

Neutron diffraction bulk texture study with impact property correlation of electron beam welded dissimilar Fe-7%Al alloy to steel joints

Present work focused on the crystallographic bulk texture study of dissimilar Fe-7percentage Al alloy to mild steel joints by electron beam welding using time-of-flight neutron diffraction technique. Textural properties directly correlated with V-notch Charpy impact study. Different processing conditions like the use of beam oscillation and by changing welding speed on texture change and its impact on the performance of the joint was evaluated. Neutron diffraction was performed using general material diffractometer beamline at ISIS neutron radiation source. Texture analysis and their variation obtained in terms of pole-figures, inverse pole figures and orientation distribution functions (ODFs). Beam oscillation shows a uniform and ordered textured grains in both fusion zone (FZ) and heat-affected zone (HAZ) due to more heat mixing that reduced unidirectional solidification gradient. ODF study reveals more gamma fibre components in both FZ and HAZ compared to its non-oscillating counterparts and higher welding speed joints, which predominantly shows more Goss, rotated Goss and cube/alpha fibre components. Charpy impact strength shows approximately 60% improvement in value for the joints, which was prepared by using beam oscillation whereas 20% reduction for higher welding speed condition. Also, X-ray tomography study of Charpy broke sample showed very lesser and shallow cracks and in smaller volume percentage of 0.45 compared to joints produced by the non-oscillating beam showing maximum value of 2.99%

A new route for developing ultrafine-grained Al alloy strips using repetitive bending under tension

Acknowledgments The authors would like to acknowledge the support provided by the Advanced Forming Research Centre (AFRC), University of Strathclyde (under the project AFRC_CATP_1186).Peer reviewedPublisher PD

Texture analysis with a time-of-flight neutron strain scanner

A time-of-flight (TOF) neutron strain scanner is a white-beam instrument optimized to measure diffractograms at precise locations within bulky specimens, typically along two perpendicular sample orientations. Here, a method is proposed that exploits the spatial resolution (∼1 mm) provided by such an instrument to determine in a nondestructive manner the crystallographic texture at selected locations within a macroscopic object. The method is based on defining the orientation distribution function (ODF) of the crystallites from several incomplete pole figures, and it has been implemented on ENGIN-X, a neutron strain scanner at the ISIS facility in the UK. This method has been applied to determine the texture at different locations of Al alloy plates welded along the rolling direction and to study a Zr2.5%Nb pressure tube produced for a CANDU nuclear power plant. For benchmarking, the results obtained with this instrument for samples of ferritic steel, copper, Al alloys and Zr alloys have been compared with measurements performed using conventional X-ray diffractometers and more established neutron techniques. For cases where pole figure coverage is incomplete, the use of TOF neutron transmission measurements simultaneously performed on the specimens is proposed as a simple and powerful test to validate the resulting ODF.Fil: Malamud, Florencia. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Santisteban, Javier Roberto. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Vicente Alvarez, Miguel Angel. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bolmaro, Raul Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Kelleher, Joe. ISIS Neutron and Muon Source; Reino UnidoFil: Kabra, Saurabh. ISIS Neutron and Muon Source; Reino UnidoFil: Kockelmann, Winfried. ISIS Neutron and Muon Source; Reino Unid

Preliminary paleohistological observations of the StW 573 ('Little Foot') skull

Numerous aspects of early hominin biology remain debated or simply unknown. However, recent developments in high-resolution imaging techniques have opened new avenues in the field of paleoanthropology. More specifically, X-ray synchrotron-based analytical imaging techniques have the potential to provide crucial details on the ontogeny, physiology, biomechanics, and biological identity of fossil specimens. Here we present preliminary results of our X-ray synchrotron-based investigation of the skull of the 3.67-million-year-old Australopithecus specimen StW 573 ('Little Foot') at the I12 beamline of the Diamond Light Source (United Kingdom). Besides showing fine details of the enamel (i.e., hypoplasias) and cementum (i.e., incremental lines), as well as of the cranial bone microarchitecture (e.g., diploic channels), our synchrotron-based investigation reveals for the first time the 3D spatial organization of the Haversian systems in the mandibular symphysis of an early hominin