Browsing by Author "Finlayson, TR"

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    40th Annual Condensed Matter and Materials Meeting, Charles Sturt University, Wagga Wagga, NSW, 2nd February – 5th February, 2016
    (Australian Institute of Physics, 2016-02-02) Tadich, A; Brand, HEA; Appadoo, D; Finlayson, TR; James, M
    The 40th Annual Condensed Matter and Materials Meeting was held at Charles Sturt University, Wagga Wagga, NSW from 2 - 5 February, 2016. There were 116 attendees, including international visitors from Scotland, China, Taiwan and New Zealand. A total of 10 invited and 29 contributed oral papers were presented during the two and one half days of scientific sessions. There were also two sessions with a total of 70 poster presentations. All presenters were invited to submit a manuscript (six pages for invited papers and four for contributed papers) for publication in the conference proceedings. Each manuscript was refereed by at least two anonymous reviewers who worked to a set of guidelines made available by the editor. Each accepted publication therefore satisfies the requirements for classification as a refereed conference publication (E1). The organizers would like to thank the reviewers for their time and effort in reviewing manuscripts, which resulted in 10 papers being accepted for publication.
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    Anomalous precursive behaviour for the martensitic material Ni 0.625 Al 0.375
    (Australian Institute of Physics, 2011-02-02) Finlayson, TR; Danilkin, SA; Studer, AJ; Whitfield, RE
    NixAl1-x alloys for 0.615 < x < 0.64 undergo a martensitic transformation upon cooling from a CsCl-type structure to a pseudo-orthorhombic structure [1]. The transformation temperature is extremely composition dependent [2] and for Ni0.625Al0.375 is ~ 80 K [1]. In previous research using an approximate cube of single crystal having x = 0.625 [3], significant strain anisotropy was detected above 80 K. It was suggested that this anomalous strain anisotropy indicated the presence of a martensite precursor within the cubic “parent” phase. The aim of the current research project is to investigate the precursive structural behaviour in the above Ni0.625Al0.375 single crystal using both elastic and inelastic neutron scattering. Results from initial experiments at both the Wombat and Taipan instruments at the Opal Research Reactor will be presented and discussed in relation to previously published strain anisotropy data determined using variable temperature, capacitance dilatometry [3].
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    Development of a new instrument to observe time-resolved neutron diffraction intensities in association with phase transitions
    (Australian Institute of Physics, 2005-01-31) Daniels, JE; Studer, AJ; Finlayson, TR; Hagen, ME
    The study of time-resolved diffraction intensities during a phase transition is important for gaining an understanding of the kinetics involved. Unfortunately the flux needed in order to achieve good counting statistics for a diffraction experiment during a single phase transition is very high. This problem is then compounded if the time scales which need to be observed are very small. Therefore techniques which can take advantage of the reversibility of some phase transitions are potentially beneficial in order to build up statistics. Stroboscopic techniques have been used in recent times to observe diffraction peak intensities with very good time resolution during the application of some type of perturbing field, driving a transition. Most commonly, and as will be the case with this instrument, high electric fields are used to switch single-crystal samples between their paraelectric and ferroelectric phases. Diffraction peaks are observed as a function of time during the switching period [1]. Other types of cycles which have also been used are stress [2], and temperature [3]. In order to carry out these types of experiments, a new capability has been added to The Australian Stress Scanner (TASS) instrument [4] at the High Flux Australian Reactor (HIFAR) operated by the Australian Nuclear Science and Technology Organisation (ANSTO). TASS is the former Triple Axis Spectrometer which, within the last couple of years, has been significantly refurbished (including the introduction of a multi-line, position-sensitive detector) to function as a two-axis diffractometer for strain mapping in engineering materials. This capability will allow for such stroboscopic experiments to be performed using the switching of high-voltage electric fields. The exact operation of the device is outlined in the experimental details section below. The common ferroelectric material, triglycine sulphate, will be used as a model crystal for the commissioning of the stroboscopic technique at HIFAR since, in a previous study involving stroboscopic diffraction intensity measurements at the ISIS [5], most unusual time dependencies for diffraction peak intensities from a TGS crystal in response to the switching of high-voltage electric fields applied to the crystal were observed.
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    Diffuse scattering studies from a martensitic Fe-Pd alloy
    (Australian Institute of Physics, 2022-12-11) Finlayson, TR; McIntyre, GJ; Rule, KC
    Results from the Koala, Taipan and Sika instruments at the OPAL reactor, ANSTO, reveal two martensitic transformations for an Fe-30at%Pd crystal between 400 to 100K. These results will be discussed in this poster presentation.
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    Diffuse scattering studies from a martensitic Fe-Pd alloy
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2020-11-11) McIntyre, GJ; Rule, KC; Finlayson, TR
    From literatrure reports, Fe-Pd alloys in the vicinity of Fe-30at%Pd exhibit two martensitic transformations on being cooled from just above room temperature to about 100K. A preliminary study of a large single crystal of this composition at the KOALA beamline, not only showed evidence for these transformations but also revealed most interesting satellite reflections around certain Bragg reflections. The crystal has been studied further in two triple-axis experiments. The first was at TAIPAN, specifically to study elastic scattering and the second, at SIKA, to study quasi-elastic scattering both in the vicinity of certain Bragg peaks but also around the satellite reflections observed at KOALA. The results from both of these experiments will be discussed. © The Authors
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    Intrinsic and extrinsic contributions to the piezoelectric effect in soft lead zirconate titanate (PZT) ceramics by time-resolved neutron diffraction
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Jones, JL; Daniels, JE; Studer, AJ; Hoffman, M; Finlayson, TR
    Piezoelectric ceramics are used in biomedical, naval, micromechanical, and many other precision engineering applications and therefore require a well-characterized, stable response. Utilizing a new capability developed on the The Australian Strain Scanner (TASS) at ANSTO, we have directly measured in situ the intrinsic and extrinsic t contributions to the piezoelectric effect in soft lead zirconate titanate (PZT) ceramics. The 002 and 200 diffraction peaks are measured as a function of time using a stroboscopic technique which enables timing resolutions of less than 30us. In other words, we have measured the 200 and 002 peak profiles as a function of time during piezoelectric activation. In this tetragonal crystal structure, a comparison of the 002 and 200 integrated intensity yields the non-180° domain switching contribution (extrinsic) while shifting of the peaks yields the change in 001 and 100 lattice strains (intrinsic). Both components lead to the macroscopic strain measured as the piezoelectric response, which is found to be a function of frequency and applied electric field. These results go toward explaining the nonlinearities of piezoelectric response versus frequency and magnitude of driving field measured in earlier work. © The Authors
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    Investigation of reference samples for residual strain measurements in a welded specimen by neutron and synchrotron x-ray diffraction
    (Elsevier, 2006-11-15) Paradowska, AM; Finlayson, TR; Price, JWH; Ibrahim, R; Steuwer, A; Ripley, MI
    In this research, both neutron and synchrotron X-ray diffraction techniques have been used to investigate variations in measured d spacing in two reference samples. The reference “stress-free” samples, a set of cubes and a comb sample, were produced using electro-discharge machining (EDM) to obtain a macro-strain-relieved condition. It is shown that there is a variation in microstructure across the parent metal, heat-affected zone (HAZ) and weld metal. A study of the issues in using the cubes and comb sample to provide reference d0 values for the measurement of residual stress in welding is presented. © 2006 Elsevier B.V.
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    Investigation of residual stress in multi-bead on plates
    (Australian Institute of Physics, 2006-02-07) Paradowska, AM; Price, JWH; Finlayson, TR; Ibrahim, R; Belvins, R; Ripley, MI
    The neutron diffraction technique is used to investigate and compare the residual stress characteristics in fully restrained samples with different numbers of beads. The aim of the research was to characterize the residual stress distribution which arises in a welded component with increasing the number of passes or beads. These results support the concept that welding integrity can be increased as additional layers of welding are added
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    Investigation of strain-free reference for residual strain measurements in a weldments by neutron and synchrotron diffraction
    (Elsevier B. V., 2005-11-27) Paradowska, AM; Finlayson, TR; Price, JWH; Ibrahim, R; Steuwer, A; Ripley, MI
    The measurement of residual strain using diffraction techniques relies on the determination of a change in lattice parameter relative to reference or 'strain free' lattice parameter. Elucidating a relevant reference lattice parameter is the most important part of any diffraction-based, residual strain experiment. In this research, neutron and synchrotron diffraction techniques have been used to investigate the strain distribution in strain reference samples used to establish the residual stresses due to welding. It is shown that there is a variation in measured diffraction angles along the length of the weld, in particular for a parent metal, heat-affected zone (HAZ) and weld metal. The stress-free samples, cuboid and a comb sample, were produced A study of the issues in using the cubes and comb sample, were produced using electro-discharge maching (EDM) to obtain a macro-strain relieved condition and reveal information about microstructural and intergranular strain variations, residual stress in welding is presented. A study is presented of the application of a strain-free cuboid and a comb sample in the flux-cored arc welding (FCAW) process
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    The martensitic transformation in In-Tl alloys revisited.
    (Australian Institute of Physics, 2019-02-05) Finlayson, TR; McIntyre, GJ; Rule, KC; Saxena, A
    The traditional view for the martensitic transformation in In-xat%Tl alloys, for 15.5 ≤ 𝑥 ≤ 30.5 was via a double shear such as: (101) [101]; (011) [011], on the basis of optical microscopy observations and measurements of the (𝑐11 - 𝑐12)/2 elastic constant. However, this model was called into question following recent low-ζ measurements of the [ζζ0][ζζ0] phonons. An alternative model for the formation of coherent nuclei and growth along conjugate {111} planes was once proposed by Geisler. This model is consistent with some electron diffuse scattering data as well as yielding identical x-ray pole figure results as those for the double-shear mechanism. Appropriate nuclei could be generated by 〈111〉 〈112〉 atomic displacements. To test such an idea we have measured the [ζζζ]T phonon branch for a good quality In-Tl crystal in a recent experiment using the cold-triple axis facility, SIKA, at the OPAL Research Reactor. These results will be reported and compared with the predictions of a model for the dynamical behaviour of coherent interfaces and modulated structures based on topological solitons, first introduced by Barsch and Krumhansl and applied to the twins accompanying martensitic transformations.
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    The martensitic transformation in indium-thallium alloys
    (Springer Nature, 2018-04-12) Finlayson, TR; McIntyre, GJ; Rule, KC
    The martensitic transformation in indium-thallium alloys is reviewed with a focus on the nature of the transformation as has been investigated using elastic and lattice vibrational properties. Recent measurements from thermal-neutron Laue and cold-neutron, triple-axis experiments are presented in an attempt to ratify the traditional explanation for the transformation as being driven by phonon softening for low-ζ [ζζ0][ζζ¯0] (i.e., T1) phonons. No evidence for phonon softening has been found to as low as ζ = 0.02 reciprocal lattice units on the T1 phonon branch. An alternative mechanism is advanced, for the transformation involving nucleation and growth on {111} planes, which appears to be consistent with electron diffuse scattering in the system. Such a mechanism is also consistent with the transition being driven by the electronic free energy of the system, as has been demonstrated by other properties. © The Minerals, Metals & Materials Society 2018
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    Mechanical properties of tungsten copper composites: direct measurement by neutron diffraction
    (Australian Institute of Physics, 2014-02-04) Mignone, PJ; Finlayson, TR; Kabra, S; Zhang, SY; Franks, GV; Riley, DP
    The composite W-10 wt%Cu (19.35% by volume, assuming negligible porosity) has been studied using the ENGIN-X beamline at the ISIS pulsed neutron source at the Rutherford Appleton Laboratory. An as-machined, compression sample was initially measured in order to check for the presence of residual stresses in the composite, using a mixed powder sample of the same elemental weight fractions as the “zero stress” comparison. Then a series of mechanical tests were carried out on the composite for applied compressive loads up to 250 MPa at both room temperature and 100ºC and compared with similar tests carried out on pure tungsten and copper samples. Residual stress values of -280 MPa (for the tungsten matrix) and 480 MPa (for the copper particulate phase) were measured for the as-machined sample. This is a surprising result, given that the yield stress for copper is typically less than 100 MPa but is not inconsistent with residual stresses reported in the literature for W-Cu composites. The mechanical properties for the composite have also been determined from the results of these in-situ, mechanical tests and compared with finite element calculations based on microstructural models for the composite material.
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    Neutron diffraction determination of macro and microstresses in an Al-Si-Mg composite and observed changes with plastic strain
    (Australian Institute of Physics, 2012-02-02) Davidson, CJ; Finlayson, TR; Griffiths, JR; Luzin, V; Wang, QG; Rajakesari, J; Llorca, J
    Neutron diffraction has been used to measure macro- and microstress components as functions of position within tension and compression samples of an Al-Si-Mg composite. The influences on these components of both tensile and compressive plastic deformation have been studied. Deformation to about 1.5% plastic strain (for both tension and compression) relieves the macrostress and most of the thermal microstress but sets up new residual microstresses. The results for the microstresses measured for the silicon phase following plastic deformation and unloading, are compared with the predictions of a finite-element model for the micromechanical behaviour of the alloy.
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    Neutron diffraction studies of the ferroelectric/paraelectric transition in triglycine sulphate
    (Australian Institute of Physics, 2005-01-31) Daniels, JE; Piltz, RO; Hagen, ME; Finlayson, TR
    This research is a preliminary study in preparation for relaxation measurements using the stroboscopic neutron diffraction technique being presented at this congress. Triglycine sulphate, TGS, is a ferroelectric material with important potential for its pyroelectric applications. However, despite a number of structural studies of TGS in the literature, many have been done using x-ray diffraction and so uncertainty remains in regards to the precise hydrogen atom positions and the role of hydrogen bonding in the transition to the ferroelectric state. In this paper, structural studies using single-crystal neutron diffraction at temperatures in the vicinity of the Curie temperature, will be presented. © (2005) Australian Institute of Physics.
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    Neutron diffraction study of polycrystalline Ca1−xSrxTiO3 mixed perovskite materials
    (Elsevier B. V., 2006-11-15) Daniels, JE; Elcombe, MM; Finlayson, TR; Vance, ER
    Mixed perovskite samples, Ca1−xSrxTiO3, produced as solid ceramic materials, have been characterized using dynamic modulus and internal friction. These provide evidence for structural instabilities which have then been studied in detail using high-resolution neutron diffraction at particular temperatures using selected samples. Structural refinements indicate a low-temperature structural distortion to an orthorhombic Pbcm structure doubled along the c-axis. Details of the results and their analysis are presented and discussed in relation to other literature data for these mixed perovskite systems. © 2006 Elsevier B.V.
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    Neutron diffraction study of polycrystalline Ca1−xSrxTiO3 mixed perovskite materials
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Daniels, JE; Elcombe, MM; Finlayson, TR; Vance, ER
    The mixed perovskite samples, Ca1−xSrxTiO3, produced as solid ceramic materials, have been characterized using dynamic modulus and internal friction. These provide evidence for structural instabilities which have then been studied in detail using high-resolution neutron diffraction at particular temperatures using selected samples. Structural refinements indicate a low-temperature structural distortion to an orthorhombic Pbcm structure doubled along the c-axis. Details of the results and their analysis are presented and discussed in relation to other literature data for these mixed perovskite systems. © The Authors
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    Neutron diffraction study of the polarization reversal mechanism in [111](c)-oriented Pb(Zn1/3Nb2/3)O-3-xPbTiO(3).
    (American Institute of Physics, 2007-05-24) Daniels, JE; Finlayson, TR; Davis, M; Damjanovic, D; Studer, AJ; Hoffman, M; Jones, JL
    The polarization reversal mechanism in [111](c)-oriented Pb(Zn1/3Nb2/3)O-3-xPbTiO(3) has been investigated by in-situ neutron diffraction. Stepwise static-field measurements of the (222)(c) rocking curves confirm a two-stage polarization reversal mechanism via a sequence of non-180 degrees domain reorientations. The time-resolved response has also been measured upon application of a bipolar square wave with a 30 s period to observe directly the relaxation times of diffracted neutron intensity during the reversal process. Upon application of a large antipolar field, the diffraction intensity increases quickly, before relaxing over a longer time period with an exponential decay constant, tau, of approximately 5.7 s. These large time constants correlate with a frequency dependence of the macroscopic strain-field response. © 2007, American Institute of Physics
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    A novel multi-scale modelling approach for determining the bulk properties of difficult-to-characterise composites
    (Australian Institute of Physics, 2013-02-05) Mignone, PJ; Wang, M; Finlayson, TR; Echlin, MP; Mottura, A; Pollock, TM; Riley, DP; Franks, GV
    A multi-scale modelling approach is presented for determining the bulk properties of copper-infiltrated Tungsten (W-Cu). A three-dimensional (3D) data-set of the W-Cu microstructure was generated using a novel serial-sectioning instrument. The image data were then reconstructed into a 3D Finite Element (FE) mesh. This made it possible to determine the bulk properties of W-Cu by simulating a representative volume of the microstructure.
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    Phase transformations in the Ca1-xSrxTiO3 perovskite system
    (Australian Institute of Physics, 2004-02-04) Daniels, JE; Elcombe, MM; Finlayson, TR; Vance, ER
    The mixed perovskite Ca1-xSrxTiO3 is one of the major constituent phases of SYNROC, a synthetic rock form proposed for the long term immobilisation of high-level nuclear waste [1]. A complete understanding of the crystal structures formed, and transitions within, each of the constituent phases is of vital importance to gaining a complete knowledge of the overall structural stability of SYNROC. This study investigated the transition temperatures and the space group symmetry of several samples between the composition values of x = 0.6 to 0.85. Previous studies of this compound have produced many conflicting results. It is believed that the reason for this is the sample preparation technique coupled with the form of the sample during experimentation, i.e., powder vs. polycrystalline solid. This study has attempted to produce samples using techniques closely related to those used in bulk SYNROC manufacture and to analyse these samples in their polycrystalline form as they would exist in SYNROC. Transition temperatures were determined by observing the dynamic Young’s modulus and internal friction of the samples between 4K and 420K using the Piezoelectric Ultrasonic Composite Oscillator Technique [2]. Classifications of the crystal structures formed were carried out using the High Resolution Powder Diffractometer at the Lucas Heights Research Reactor within the temperature range of 8K to 300K. Space group symmetries for each phase were then determined by Rietveld refinement.
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    Residual stress distribution in steel butt welds measured using neutron and synchrotron diffraction
    (Institute of Physics, 2009-03-25) Paradowska, AM; Price, JWH; Finlayson, TR; Lienert, U; Walls, P; Ibrahim, R
    70 keV synchrotron radiation and thermal neutrons have been employed to investigate the residual stress characteristics in a fully restrained, steel, butt weld. The focus is on the values of the subsurface and through-thickness strain/stress variation in the middle of the weld. The advantages and limitations of the techniques have been addressed, in relation to the gauge volume, the stress-free reference sample and positioning. The measurement of residual stress around the weld achieved in this work significantly improves the resolution at which residual stress in welded components has been determined. © 2009, Institute of Physics