ANSTO :: Browsing by Author "Callaghan, MD"

Browsing by Author "Callaghan, MD"

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Deformation mechanisms of twinning-induced plasticity steels: in situ synchrotron characterization and modeling
(Elsevier, 2010-03) Yan, K; Carr, DG; Callaghan, MD; Liss, KD; Li, HJ
The plastic deformation behavior of twinning-induced plasticity steels of composition Fe-25Mn-3Si-3Al are investigated by means of in situ synchrotron high-energy X-ray diffraction and compared to self-consistent simulations. It is the first time the alternating interaction of {1 1 1} <1 1 0> slip and {1 1 1} <1 1 2> twinning have been directly observed in situ while undergoing uniaxial tension. The deformation texture is determined mainly by dislocation gliding, while deformation twinning impedes the reinforcement of texture. © 2010, Elsevier Ltd.
Energy-based approach for the evaluation of low cycle fatigue behaviour of 2.25Cr-1Mo steel at elevated temperature
(Elsevier, 2010-08-20) Callaghan, MD; Humphries, SR; Law, M; Ho, M; Bendeich, PJ; Li, HJ; Yeung, WY
The energy-based approach for the evaluation of low cycle fatigue behaviour of 2.25Cr–1Mo steel at elevated temperature has been investigated and detailed analyses discussed. Plastic strain energy was determined per cycle and found to characterise both crack initiation and propagation to failure regimes. At cyclic stabilisation, average plastic strain energy may be used as a suitable damage parameter and correlations between experimental and predicted data determined. The fatigue toughness to failure of the material was established and the development of a fatigue toughness to crack propagation analysis is presented. © 2010, Elsevier Ltd.
Evaluation of high temperature fatigue behaviour of P22 by miniature specimen testing
(Trans Tech Publications, 2010-01-01) Callaghan, MD; Humphries, SR; Law, M; Li, HJ; Yeung, WY
Miniature specimen testing to evaluate mechanical properties, presents a novel opportunity to undertake structural integrity assessments of in-service power generation components, by removing only a very small volume of material. In this study, high temperature fatigue testing of P22 steel was undertaken and a number of fatigue properties determined using a miniature specimen testing methodology. Good comparisons were observed between fatigue properties determined by miniature specimens and the more established standard-sized specimen testing reported in literature.
Hydrogen-induced microstructure, texture and mechanical property evolutions in a high-pressure torsion processed zirconium alloy
(Elsevier Ltd., 2012-11-01) Wang, Z; Garbe, U; Li, HJ; Studer, AJ; Harrison, RP; Callaghan, MD; Wang, Y; Liao, XZ
The gaseous hydriding-induced evolutions of the microstructure, texture and mechanical properties of Zircaloy-4 processed by high-pressure torsion (HPT) were assessed. Much delta-ZrH(1.66) precipitation at 15 atm (21%) incurred significant hardening of vacuum-annealed HPT samples, and pure epsilon-ZrH(2) obtained at 20 atm showed a superior microhardness of 470 HV(0.3) and a low fracture toughness of 0.63 MPa m(1/2). The delta-hydrides presented strong (1 1 1) texture and followed the (0 0 0 1)(alpha-Zr)//{1 1 1}(delta-ZrH1.66) orientation relationship with the alpha-Zr matrix. During hydriding, alpha-Zr recrystallization texture was developed from the initial deformation texture. Copyright © 2012 Acta Materialia Inc.
Martensitic phase transformation and deformation behavior of Fe–Mn–C–Al twinning-induced plasticity steel during high-pressure torsion
(Wiley Online Library, 2014-02-05) Yan, K; Bhattacharyya, D; Lian, Q; Kabra, S; Kawasaki, M; Carr, DG; Callaghan, MD; Avdeev, M; Li, HJ; Wang, Y; Liao, XZ; Langdon, TG; Liss, KD; Dippenaar, RJ
The transformation between the face centered cubic austenitic and hexagonal close-packed martensitic phases during high-pressure torsion processing was observed in a Fe–Mn–C–Al twinning-induced plasticity steel. This phase transformation was not found in the same material processed by unidirectional compressive and tensile deformation. Initiated by the high-pressure loading, the martensite phase initially increased with torsional strain but diminished subsequently. Texture evolution of the austenitic phase was compared with the ideal texture distribution of face-centered cubic materials after shear deformation.© 2014, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Measurement of fracture toughness of hydrided Zircaloy - 4.
(The Institute of Materials Engineering Australasia Ltd., 2004) Callaghan, MD; Yeung, WY; Ripley, MI; Carr, DG
Zircaloy-4 is a zirconium alloy that will be used for construction of many of the core components in the replacement research reactor at Lucas Heights. The fracture toughness of the alloy and its radiation-induced reduction over the 40 year planned life of the reactor is an important mechanical property for this application. This study aims to simulate the radiation-induced reduction in fracture toughness by hydriding Zircaloy-4. A range of fracture toughnesses is required to calibrate the sub-size Charpy and small punch (SP) surveillance specimens that will be irradiated over the life of the reactor against standard J1C fracture toughness specimens. Pieces of Zircaloy-4 plate were hydrided in a vessel at a temperature of 520°C, at different pressures for either 10 or 22 hours. Final hydrogen concentrations between 25 wt% ppm and 380 wt% ppm hydrogen were obtained under gaseous atmosphere. The fracture toughness of the hydrided Zircaloy-4 was assessed using sub-size 2.5 mm-thick Charpy, three-point bend J1C and SP tests. The results were correlated to determine the relationship between the J-integral fracture toughness, Charpy impact energy and equivalent fracture strain (εqf) from the SP tests. It was found that as hydrogen concentration and hydride formation increased, the fracture toughness of the alloy generally decreased. The results show there to be a useful relationship between fracture toughness and εqf measured for the SP tests.
Microstructural evolution during gaseous hydrogen charging of Zircaloy-4 processed by high-pressure torsion: a comparative study
(Elsevier B.V., 2012-02-01) Wang, ZY; Li, HJ; Garbe, U; Callaghan, MD; Wang, Y; Liao, XZ
The original and high-pressure torsion (HPT) processed Zircaloy-4 materials were hydrided using gaseous hydrogen charging at different hydrogen pressures (10, 15 and 20 atm). The phase and microstructural evolutions of the samples during hydriding were characterized. It showed that when hydriding at the identical conditions, more hydrides tended to form in the HPT samples compared to that of the original ones. At a hydrogen pressure of 20 atm, the HPT sample was completely converted to epsilon-ZrH2 while some delta-ZrH1.66 hydrides (volume fraction similar to 5.73%) were present in the material without HPT preprocessing. The HPT samples exhibited high potential for the hydride precipitation, and the large concentration of lattice defects induced by HPT was considered to be responsible for this enhanced susceptibility. © 2011 Elsevier B.V.
On the compression behavior of an austenitic Fe-18Mn-0.6C-1.5Al twinning-induced plasticity steel
(Wiley, 2013-06-20) Peng, CT; Callaghan, MD; Li, HJ; Yan, K; Liss, KD; Ngo, TD; Mendis, PA; Choi, CH
High manganese austenitic TWIP steels are of great potential in the field of transportation-related industries owing to their exceptional combination of strength and ductility. A series of compression experiments were conducted on a Fe–18Mn–0.6C–1.5Al alloy at various strain rates (from 1.0 × 10−2 to 6.4 × 103 s−1) and total strains (≈15 and ≈20%) with a Gleeble 3500 thermo-mechanical simulator and a Split Hopkinson Pressure Bar system. Under compressive deformation, results showed this alloy possessed excellent strain-hardening behavior, attributed to the occurrence of mechanical twinning during deformation. The prevailing deformation mechanism was observed to be twinning, which was substantiated by microstructural analyses, as well as phase identification and evolution of crystallographic texture. Copyright © 1999-2020 John Wiley & Sons, Inc.
Special testing equipment and validation of measurement methodologies for high temperature low cycle fatigue testing of miniature metallic specimens
(Springer Nature, 2016-02-25) Callaghan, MD; Humphries, SR; Law, M; Bendeich, PJ; Yeung, WY
A technique for high temperature low cycle fatigue testing of metallic materials has been developed, to determine fatigue behaviour through the testing of miniature specimens. The miniature specimen geometry was specifically designed, such that it could be manufactured from a small volume of material removed by chain-drilling extraction. An extensometry method to measure and control strain at the specimen shoulders during testing was adopted. This was undertaken to minimise the deleterious contact effects that can occur via extensometry attached at the gauge length of specimens, hence leading to premature failure and inaccurate fatigue data. By the application of this technique, the high temperature low cycle fatigue behaviour of 2.25Cr-1Mo steel was successfully characterised at 540 °C, under a fully reversed strain-controlled regime. The fatigue properties of the steel obtained from testing miniature specimens were shown to correlate well with existing literature for the material under comparable conditions, as determined by the testing of conventional standard-sized specimens. © 2016 Society for Experimental Mechanics
Specimen-size dependency and modelling of energy evolution during high-temperature low-cycle fatigue of pressure vessel steel
(Elsevier Ltd., 2011-08-01) Callaghan, MD; Humphries, SR; Law, M; Ho, M; Yan, K; Yeung, WY
High-temperature low-cycle fatigue testing was conducted on pressure vessel steel using standard and miniature specimen sizes and the fatigue toughness required for macrocrack propagation was investigated. A definite specimen-size dependency was observed for both the threshold cumulative plastic strain energy and cycles required for macrocrack propagation, which was explained to be influenced by geometric conditions. An analytical modelling prediction was developed that accounted for specimen-size dependency and was successfully applied to predict fatigue toughness to macrocrack propagation. (C) 2011 Acta Materialia Inc.

Browsing by Author "Callaghan, MD"

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