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Browsing by Author "Muránsky, O"

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Advanced nuclear reactor materials research in Australia: high temperature properties, radiation effects and corrosion behaviour
(IAEA, 2020-05) Muránsky, O; Edwards, L
The Australian Nuclear Science and Technology Organisation (ANSTO) and its predecessor, the Australian Atomic Energy Commission has a long history in nuclear-based research and development. This is continuing through Australia’s recent membership of the Generation IV International Forum (GIF). As Australia’s implementing agent within GIF, ANSTO is focussing the majority of its research on nuclear materials engineering including structural performance evaluations in complex nuclear environments, advanced manufacturing, and system reliability assessment. Although this work concentrates on the Molten Salt Reactor (MSR) and Very High Temperature Reactor (VHTR) systems most of the research outcomes are applicable to a wide range of advanced nuclear reactor systems.
Annealing-induced strengthening and stabilization in ultrafine-grained Al and Al–Mg alloys prepared by rapid powder consolidation
(Elsevier, 2022-01-26) Zhou, DS; Bu, YF; Muránsky, O; Geng, HW; Sun, BH; Yang, C; Zhang, DL
Annealing usually softens Al–Mg based alloys due to grain coarsening. This work shows that annealing induces strengthening in bulk ultrafine-grained Al and Al-(2.5, 5 and 7.5) at.% Mg samples fabricated by mechanical alloying and rapid powder extrusion. Experimental investigation of the microstructure of the annealed samples reveals that the annealing promotes in-situ formation of nanoscale dispersoids which strongly suppresses grain growth and recrystallization. The in-situ formed nanodispersoids warrant high thermal stability of the ultrafine-grained matrix microstructure and improve the strength of the as-extruded samples while maintaining their good ductility. The present findings offer an exciting pathway in developing thermally stable ultrafine-grained Al–Mg based alloys with a notable combination of high strength and good ductility. © 2021 Elsevier B.V
Author Correction: Neutron diffraction analysis of stress and strain partitioning in a two-phase microstructure with parallel-aligned phases
(Springer Nature, 2020-10-07) Huang, QL; Shi, R; Muránsky, O; Beladi, H; Kabra, S; Schimpf, C; Volkova, OS; Biermann, H; Mola, J
The original version of this Article contained an error in Affiliation 5, which was incorrectly given as ‘Spallation Neutron Source, The Rutherford Appleton Laboratory, Oxfordshire, UK’. The correct affiliation is listed below: ISIS Neutron and Muon Facility, The Rutherford Appleton Laboratory, Oxfordshire, UK. This error has now been corrected in the HTML and PDF versions of the Article. © 2020 The Author(s)
The characterisation and formation of novel microstructural features in a Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS)
(Elsevier, 2021-01) Zhu, HL; Wang, ZY; Muránsky, O; Davis, J; Yu, S; Kent, D; Wang, G; Dargusch, MS
Novel microstructural features were found in the Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS). Examination of the microstructure showed that the fabricated sample exhibits a layered morphology with arced deposit boundaries. Novel distributions and morphologies of various phases including β, α, α'' and ω were detected in the LENS-manufactured part which substantially differ to conventionally processed alloy counterparts. The β grains and subgrains spread over multiple deposits and layers, aligned to the build direction, forming a complex network microstructure comprising large highly textured columnar grains aligned to β phase <001> orientations. The α precipitates have needle-like shapes and are widely distributed across a majority of the deposited layers, whereas the nanoscale ω particles were present in regions absent of α precipitation. Localised, massively transformed α'' phase with a very long and curved rod-like shape and substantial surface defects was identified. The formation of these novel microstructural features is investigated and discussed in the context of the characteristics of the LENS fabrication process. The microstructures are attributed to the complex thermal history in the unique deposit-by-deposit and layer-by-layer method employed during LENS additive manufacturing in conjunction with the complex precipitation behaviours exhibited by TiNb-based alloys. The characteristics and formation mechanisms of the LENS-manufactured Ti−Nb−Zr−Mo−Sn alloy microstructures revealed here provide a basis to optimize LENS and post-LENS heat treatment processes to optimize microstructures for improved performance. © 2020 Elsevier B.V
Combined in situ neutron diffraction and acoustic emission of twin nucleation & twin growth in extruded ZM20 Mg alloy
(Trans Tech Publications, 2009-11-10) Muránsky, O; Barnett, MR; Carr, DG; Vogel, SC; Oliver, EC
In the present work in situ neutron diffraction and acoustic emission were used concurrently to study deformation twinning in two ZM20 Mg alloys with significantly different grain sizes at room temperature. The combination of these techniques allows differentionation between the twin nucleation and the twin growth mechanisms. It is shown, that yielding and immediate post-yielding plasticity in compression is governed primarily by twin nucleation, whereas the plasticity at higher strains is governed by twin growth. The current results further suggest that yielding by twinning happens in a slightly different manner in the fine-grained as compared to the coarse-grained alloy. © Trans Tech Publications Ltd
Comprehensive numerical analysis of a three-pass bead-in-slot weld and its critical validation using neutron and synchrotron diffraction residual stress measurements
(Pergamon-Elsevier Science LTD, 2012-05-01) Muránsky, O; Smith, MC; Bendeich, PJ; Holden, TM; Luzin, V; Martins, RV; Edwards, L
The current paper presents a finite element simulation of the residual stress field associated with a three pass slot weld in an AISI 316LN austenitic stainless steel plate. The simulation is split into uncoupled thermal and mechanical analyses which enable a computationally less expensive solution. A dedicated welding heat source modelling tool is employed to calibrate the ellipsoidal Gaussian volumetric heat source by making use of extensive thermocouple measurements and metallographic analyses made during and after welding. The mechanical analysis employs the Lemaitre-Chaboche mixed hardening model. This captures the cyclic mechanical response which a material undergoes during the thermo-mechanical cycles imposed by the welding process. A close examination of the material behaviour at various locations in the sample during the welding process, clearly demonstrates the importance of defining the correct hardening and high temperature softening behaviour. The simulation is validated by two independent diffraction techniques. The well-established neutron diffraction technique and a very novel spiral slit X-ray synchrotron technique were used to measure the residual stress-strain field associated with the three-pass weld. The comparison between the model and the experiment reveals close agreement with no adjustable parameters and clearly validates the used modelling procedure. Crown Copyright (C) 2011 Elsevier Ltd.
Computational model development for additive manufacturing (AM) based laser cladding structural repairs of high strength metallic aerospace components
(Department of Defence, Defence Science and Technology Organisation, 2019-03) Walker, K; Cooper, T; Muránsky, O; Bendeich, PJ
Additive manufacturing is a revolutionary new technology with the potential to dramatically change the way aircraft structures and components are designed and manufactured. The technology is widely becoming a popular method to manufacture new and replacement parts, and it also offers a rapid and effective repair technology for military aircraft components. The supply lead time and/or cost of replacement for aircraft components can be substantial and additive manufacturing can provide a solution to both of these problems. DST Group is currently working with University and industry partners to develop additive manufacturing based solutions for the repair and manufacture of a range of Australian military aircraft components. Currently, there are two types of repair categories used. The first is where the repair damage is such that static and fatigue strength margins remain within accepted limits so as to restore the component geometry, function and surface finish properties (i.e. non-fracture critical). The second is where the damage is more significant and the repair itself carries load and is essential to restore static and fatigue strength margins. Advanced and high-fidelity numerical modelling is an essential element required for the design, substantiation and certification of structural repairs. This presentation describes recent work to develop that advanced computational modelling capability, particularly for predicting the residual stress profile in laser cladding repairs of high strength martensitic steel materials as used in high value, critical landing gear components.
Controlling oxygen defect formation and its effect on reversible symmetry lowering and disorder-to-order phase transformations in nonstoichiometric ternary uranium oxides
(American Chemical Society, 2019-04-09) Murphy, GL; Wang, CH; Zhang, Z; Kowalski, PM; Beridze, G; Avdeev, M; Muránsky, O; Brand, HEA; Gu, QF; Kennedy, BJ
In situ synchrotron powder X-ray diffraction measurements have demonstrated that the isostructural AUO4–x (A = alkaline earth metal cation) oxides CaUO4–x and α-Sr0.4Ca0.6UO4–x undergo a reversible phase transformation under reducing conditions at high temperatures associated with the ordering of in-plane oxygen vacancies resulting in the lowering of symmetry. When rhombohedral (space group R3̅m) CaUO4–x and α-Sr0.4Ca0.6UO4–x are heated to 450 and 400 °C, respectively, in a hydrogen atmosphere, they undergo a first-order phase transformation to a single phase structure which can be refined against a triclinic model in space group P1̅, δ-CaUO4–x and δ-Sr0.4Ca0.6UO4–x, where the oxygen vacancies are disordered initially. Continued heating results in the appearance of superlattice reflections, indicating the ordering of in-plane oxygen vacancies. Cooling ordered δ-CaUO4–x and δ-Sr0.4Ca0.6UO4–x to near room temperature results in the reformation of the disordered rhombohedral phases. Essential to the transformation is the generation of a critical amount of oxygen vacancies. Once these are formed, the transformation can be accessed continuously through thermal cycling, showing that the transformations are purely thermodynamic in origin. Stoichiometric structures of both oxides can be recovered by heating oxygen deficient CaUO4–x and α-Sr0.4Ca0.6UO4–x under pure oxygen to high temperatures. When heated in air, the amount of oxygen vacancy defects that form in CaUO4–x and α-Sr0.4Ca0.6UO4–x are found to correlate with the A site composition. The inclusion of the larger Sr2+ cation on the A site reduces defect–defect interactions, which increases the amount of defects that can form and lowers their formation temperature. The relative difference in the amount of defects that form can be understood on the basis of oxygen vacancy and U5+ disordering as shown by both ab initio calculations and estimated oxygen vacancy formation energies based on thermodynamic considerations. This difference in defect–defect interactions consequently introduces variations in the long-range ordered anionic lattice of the δ phases despite the isostructural relationship of the α structures of CaUO4–x and Sr0.4Ca0.6UO4–x. These results are discussed with respect to the influence the A site cation has upon anion defect formation and ordering and are also compared to δ-SrUO4–x, the only other material known to be able to undergo a reversible symmetry lowering and disorder-to-order transformation with increasing temperature. © 2019 American Chemical Society
Corrosion performance of Ni-16%wt.Mo-X%wt.SiC alloys in FLiNaK molten salt
(Elsevier, 2018-10-01) Yang, C; Muránsky, O; Zhu, HL; Karatchevtseva, I; Holmes, R; Avdeev, M; Jia, YY; Huang, HF; Zhou, XT
The corrosion performance of Ni-16%wt.Mo-X%wt.SiC (X = 0.5, 1.5, 2.0, 2.5 and 3.0) alloys prepared via mechanical alloying followed by consolidation using spark plasma sintering (SPS) from pure Ni, Mo and SiC powders is investigated. Corrosion testing at 650 °C/200 h in FLiNaK molten salt showed that increasing the volume fraction of SiC in the initial Ni-Mo-SiC powder mixture leads to formation of large amount of Mo2C precipitates, which readily dissolve into FLiNaK molten salt. Hence, only the corrosion resistance of NiMo-SiC alloys with a low SiC content (<2 wt.%) is comparable to that of Hastelloy-N® alloy. © 2018 Elsevier Ltd. All rights reserved.
Corrosion performance of Ni-based structural alloys for applications in molten-salt based energy systems: experiment & numerical validation
(Elsevier, 2021-09) Lee, M; Muránsky, O; Karatchevtseva, I; Huang, HF; Laws, KJ
The molten salt corrosion performance of a Y2O3-strengthened Ni-Cr alloy (MA754®) designed for high temperature applications (> 750 °C) was compared to purpose-designed Ni-Mo-Cr molten-salt resistant alloys (GH3535, HASTELLOY-N®). The significant material mass loss of MA754® alloy is attributed to its higher Cr-content. However, Y2O3 dispersoids are shown to play only a minor role in the corrosion performance of this oxide-dispersion-strengthened (ODS) alloy. The current result, thus, points to the possibility for the development of low Cr-content ODS alloys that combines the high-temperature properties of ODS MA754® alloy with good molten salt corrosion resistance of well-established GH3535 and HASTELLOY-N® alloys. Crown Copyright © 2021 Published by Elsevier Ltd
Deformation behavior of bulk TRIP steel
(Association for Computational Materials Science and Surface Engineering, 2015-02-02) Zrník, J; Muránsky, O; Novy, Z; Slama, P
Purpose: Experimental verification of various thermo-mechanical (TM) processing schedules, with aim to modify the structure characteristics using press forging of Si-Mn TRIP (Transformation Induced Plasticity) steel, was described. Design/methodology/approach: High strength and ductility of TRIP steels is attributed to the TRIP effect resulting from the strain induced martensitic transformation of the retained austenite in the multiphase (ferrite, bainite, martensite) microstructure. In order to rationalize the retained austenite (RA) volume fraction in steel microstructure, several TM schedules were employed at experiment where different austenite conditioning was considered. Findings: The various multiphase structure characteristics were then resulting after TM processing of steel, where different volume fractions of ferrite, bainite and RA were received in the steel. The modification of structural characteristics of steel then influenced the deformation behavior and mechanical properties TRIP steel. Research limitations/implications: The present work also focused on monitoring of RA transformation during incremental mechanical straining using in-situ neutron diffraction technique. Originality/value: This non-convenient experimental method was used to characterize the kinetics of RA transformation and its stability during consecutive straining. © 2015 International OCSCO World Press.
Development of a new powder-bed arc additive manufacturing approach for producing high entropy alloys
(Australian Nuclear Science and Technology Organisation, 2021-11-26) Dong, BS; Muránsky, O; Zhu, Hl; Muránsky, O; Wang, ZY; Reid, M; Li, HJ
High entropy alloys (HEAs) have gained significant attention over the past decade from both academic and industrial communities due to their unique design concept and promising properties. The manufacturing of this emerging material with desired properties remains challenging. Most of previous work utilized conventional vacuum arc melting and casting methods for producing HEAs. However, the disadvantage of typical casting microstructure, columnar dendrite and serious chemical segregation, causes serious deterioration to their mechanical properties. A new powder-bed arc additive manufacturing (PAAM) has been developed at the University of Wollongong for producing HEAs. This approach, with a high level of flexibility for controlling the forming process and the characteristic rapid solidification, enables the tailoring of the microstructure through the process control and the effective reduction of the chemical segregation in these compositionally complexed alloys. Additionally, compared with the laser and electron beam based additive manufacturing, PAAM is advantageous for higher production rate hence it is promising in industrial applications for producing bulk components in shorter period. The production of a eutectic AlCoCrFeNi2.1 HEA using this new PAAM approach will be presented to demonstrate its capability. The characterisation work shows that the produced AlCoCrFeNi2.1 samples have a lamellar microstructure consisting of the soft but ductile face-centered cubic (FCC) phase as well as the hard body-centered-cubic (BCC) phase. The material demonstrates a remarkable combination of excellent ultimate tensile strength (719 MPa) and ductility (elongation ~27%). The current work has demonstrated that the developed PAAM process is promising for producing HEA components with desired properties. © The Authors
The effect of applied stress on the high-temperature creep behaviour and microstructure of NiMoCr Hastelloy-N® alloy
(Elsevier, 2021-05) Zhu, HL; Muránsky, O; Wei, T; Davis, J; Budzakoska-Testone, E; Huang, HF; Drew, M
The high-temperature creep behaviour and microstructural evolution of Hastelloy-N® was investigated using miniaturised creep samples tested under vacuum at 973 K (700 °C) and stresses of 100 MPa and 165 MPa. The higher applied stress reduced the creep life of the alloy sevenfold, and the creep mechanism at 165 MPa was predominately dislocation-creep while the creep mechanism at 100 MPa was a combination of dislocation creep, diffusion creep and grain boundary sliding. The post-creep microstructure examination using Electron Back-Scatter Diffraction (EBSD) technique showed significantly larger number of Low-Angle Grain Boundaries (LAGBs) and Geometrically-Necessary Dislocations (GNDs) formed during creep at 165 MPa than at 100 MPa. On the other hand, the microstructure of the sample tested at 100 MPa revealed more pronounced precipitation of secondary carbides along High-Angle Grain Boundaries (HAGBs) due to the longer exposure to high temperature. The precipitation of secondary carbides along grain boundaries resulted in grain boundary embrittlement and the promotion of intergranular cracking, which then resulted in low strain-to-failure in the low-stress creep test sample. In addition, it is shown that the prolonged exposure to the elevated temperature lead to Cr depletion from the matrix, reducing solid solution strengthening during creep. © 2021 Acta Materialia Inc. Published by Elsevier B.V.
The effect of microstructure and welding-induced plasticity on the strength of Ni–Mo–Cr alloy welds
(Elsevier, 2021-06) Danon, AE; Muránsky, O; Zhu, HL; Wei, T; Flores-Johnson, EA; Li, ZJ; Kruzic, JJ
The mechanical performance of a Ni–Mo–Cr (GH3535) alloy weldment, produced using a matching filler metal, was assessed and compared to the surrounding parent metal. Ambient-temperature mechanical characterisation included hardness testing, small punch testing and uniaxial tensile testing, while a crystal plasticity finite element model was used to assess the impact of crystallographic texture on the mechanical properties. Despite the similar chemical composition, the weld metal exhibited superior strength and ductility to that of the parent metal. The higher strength was primarily attributed to the high dislocation density in the weld metal imbued by the welding-induced thermo-mechanical loading. In contrast, the ductility difference was attributed to M6C carbide stringers in the parent metal that initiated fracture at lower strains when compared to the weld metal, with the latter containing finer, well-dispersed M6C carbides. © 2021 Acta Materialia Inc. Published by Elsevier B.V.
The effect of milling time on the microstructural characteristics and strengthening mechanisms of NiMo-SiC alloys prepared via powder metallurgy
(Multidisciplinary Digital Publishing Institute, 2017-04-06) Yang, C; Muránsky, O; Zhu, HL; Thorogood, GJ; Avdeev, M; Huang, HF; Zhou, XT
A new generation of alloys, which rely on a combination of various strengthening mechanisms, has been developed for application in molten salt nuclear reactors. In the current study, a battery of dispersion and precipitation-strengthened (DPS) NiMo-based alloys containing varying amounts of SiC (0.5–2.5 wt %) were prepared from Ni-Mo-SiC powder mixture via a mechanical alloying (MA) route followed by spark plasma sintering (SPS) and rapid cooling. Neutron Powder Diffraction (NPD), Electron Back Scattering Diffraction (EBSD), and Transmission Electron Microscopy (TEM) were employed in the characterization of the microstructural properties of these in-house prepared NiMo-SiC DPS alloys. The study showed that uniformly-dispersed SiC particles provide dispersion strengthening, the precipitation of nano-scale Ni3Si particles provides precipitation strengthening, and the solid-solution of Mo in the Ni matrix provides solid-solution strengthening. It was further shown that the milling time has significant effects on the microstructural characteristics of these alloys. Increased milling time seems to limit the grain growth of the NiMo matrix by producing well-dispersed Mo2C particles during sintering. The amount of grain boundaries greatly increases the Hall–Petch strengthening, resulting in significantly higher strength in the case of 48-h-milled NiMo-SiC DPS alloys compared with the 8-h-milled alloys. However, it was also shown that the total elongation is considerably reduced in the 48-h-milled NiMo-SiC DPS alloy due to high porosity. The porosity is a result of cold welding of the powder mixture during the extended milling process. © This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Effect of tellurium (Te4+) irradiation on microstructure and associated irradiation-induced hardening
(IOP Publishing, 2021-04) Huang, HF; Liao, JZ; Lei, GH; Muránsky, O; Wei, T; Ionescu, M
The GH3535 alloy samples were irradiated using 15-MeV Te4+ ions at 650 °C to a dose of 0.5, 3.0, 10, and 20 dpa, respectively. The Te atoms distribution and microstructure evolution were examined by electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The nano-indenter was then used to measure the nano-hardness changes of samples before and after irradiation. TEM results showed the formation of dislocation loops in the irradiated samples. Their mean diameters increase with the increase of irradiation dose and tends to be saturated when irradiation dose exceeds 10 dpa. The ratio of yield strength increments calculated by dispersed barrier hardening (DBH) model is basically consistent with that of nano-hardness increments measured by nano-indenter. In addition, the relationship between the nano-hardness increments and dpa for the GH3535 alloy irradiated by Te ions has been revealed in the study. © 2021 Chinese Physical Society and IOP Publishing Ltd
Effects of post heat treatment on the microstructure and mechanical properties of wire arc additively manufactured Hastelloy C276 alloy
(Elsevier, 2021-07) Qiu, ZJ; Wu, BT; Wang, ZY; Wexler, D; Carpenter, K; Zhu, HL; Muránsky, O; Zhang, JR; Li, HJ
Post-processing is often inevitable for most additively manufactured components in order to improve material properties and product quality. In this study, the influence of post-heat treatments (PHTs) at 871 °C and 1177 °C on the microstructure and mechanical properties of a nickel-base Hastelloy C276 alloy prepared using wire arc additive manufacturing (WAAM) were investigated. The results showed that after a PHT at 871 °C, the as-built alloy was strengthened due to the formation of a large amount of Mo-rich nano-sized μ phase in the interdendritic areas. This was at the expense of a significant ductility loss. In contrast, no μ phase precipitates were observed after PHT at 1177 °C. Furthermore, the 1177 °C treatment led to the dissolution of the Mo-rich p phase which was present in the as-built sample, increased solid-solution strengthening, and improvements in both strength and ductility concurrently. This study enables an improved understanding of post-processing-microstructure-property inter-relationships for Hastelloy C276 alloy prepared by WAAM, providing guidelines for further microstructure optimization through PHT to improve the material's mechanical properties. © 2021 Elsevier Inc.
Energy-resolved neutron imaging options at a small angle neutron scattering instrument at the Australian Center for Neutron Scattering
(AIP Publishing, 2019-03-26) Tremsin, AS; Sokolova, AV; Salvemini, F; Luzin, V; Paradowska, AM; Muránsky, O; Kirkwood, HJ; Abbey, B; Wensrich, CM; Kisi, EH
Energy-resolved neutron imaging experiments conducted on the Small Angle Neutron Scattering (SANS) instrument, Bilby, demonstrate how the capabilities of this instrument can be enhanced by a relatively simple addition of a compact neutron counting detector. Together with possible SANS sample surveying and location of the region of interest, this instrument is attractive for many imaging applications. In particular, the combination of the cold spectrum of the neutron beam and its pulsed nature enables unique non-destructive studies of the internal structure for samples that are opaque to other more traditional techniques. In addition to conventional white beam neutron radiography, we conducted energy-resolved imaging experiments capable of resolving features related to microstructure in crystalline materials with a spatial resolution down to ∼0.1 mm. The optimized settings for the beamline configuration were determined for the imaging modality, where the compromise between the beam intensity and the achievable spatial resolution is of key concern. © 2020 AIP Publishing LLC
Evaluation of residual stresses in electron-beam welded Zr2.5Nb0.9Hf Zircadyne flange mock-up of a reflector vessel beam tube flange
(Elsevier Science BV., 2013-07-01) Muránsky, O; Holden, TM; Kirstein, O; James, JA; Paradowska, AM; Edwards, L
The dual-phase alloy Zr2.5Nb alloy is an important nuclear material, because of its use in current and possible use in future nuclear reactors. It is, however, well-known that Zr2.5Nb weldments can fail through a time-dependent mechanism called delayed hydride cracking which is typically driven by the presence of tensile residual stresses. With a view to understanding the development of residual stresses associated with Zr2.5Nb welds the current study focuses on the evaluation of the residual stresses in a mock-up of a reactor beam tube flange made from Zr2.5Nb0.9Hf. The present results suggests that, like ferritic welds which undergo a solid-state phase transformation upon welding, Zr2.5Nb0.9Hf welds also develop high tensile residual stresses in the heat-affected zone whereas the stresses closer to the weld tip are reduced by the effects of the beta -> alpha solid-state phase transformation. © 2013, Elsevier Ltd.
Fracture and fatigue behaviour of a laser additive manufactured Zr-based bulk metallic glass
(Elsevier, 2020-12) Best, JP; Ostergaard, HE; Li, BS; Stolpe, M; Yang, F; Nomoto, K; Hasib, MT; Muránsky, O; Busch, R; Li, XP; Kruzic, JJ
Laser additive manufacturing of bulk metallic glass (BMG) provides an effective bypassing of the critical casting thickness constraints that limit the size of components that can be produced; however, open questions remain regarding the resulting mechanical properties. In this work, a Zr-based BMG known as AMZ4 with composition Zr59.3Cu28.8Nb1.5Al10.4 was printed using a laser powder bed fusion (LPBF) technique. Micro X-ray computed tomography results together with electron microscopy imaging revealed porous processing defects in LPBF produced AMZ4 that led to a loss in tensile strength. Fatigue crack growth studies revealed a fatigue threshold, ΔKth., of ∼1.33 MPa√m and a Paris law exponent of m = 1.14, which are relatively low values for metallic materials. A KIC fracture toughness of 24−29 MPa√m was found for the LPBF BMG samples, which is much lower than the KQ of 97−138 MPa√m and KJIC of 158−253 MPa√m measured for the cast alloy with the same composition. The lower fracture toughness of the laser processed AMZ4 was attributed to ∼7.5× higher dissolved oxygen in the structure when compared to the cast AMZ4. Despite the higher level of oxygen, the formation of oxide nanocrystals was not observed by transmission electron microscopy. Oxygen induced toughness loss was confirmed by dissolving elevated concentrations of oxygen into cast AMZ4 rods, which led to a reduction in bending ductility and changes in the short-range order of the glass structure, as revealed by synchrotron X-ray diffraction. © 2020 Elsevier B.V.

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