ORCID Profile
0000-0002-2420-3879
Current Organisation
UNSW Sydney
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Metals and Alloy Materials | Materials Engineering | Ceramics | Materials engineering | Manufacturing Engineering | Machining | Metals and alloy materials |
ANZSRC Socio-Economic Objective (SEO)
Machined Metal Products | Semi-Finished Metal Products | Structural Metal Products | Fabricated Metal Products not elsewhere classified | Basic Copper Products
Related Links
Publications
Mechanical adaptability of the Bouligand-type structure in natural dermal armour
Publisher: Springer Science and Business Media LLC
Date: 15-10-2013
DOI: 10.1038/NCOMMS3634
Abstract: Arapaima gigas, a fresh water fish found in the Amazon Basin, resist predation by piranhas through the strength and toughness of their scales, which act as natural dermal armour. Arapaima scales consist of a hard, mineralized outer shell surrounding a more ductile core. This core region is composed of aligned mineralized collagen fibrils arranged in distinct lamellae. Here we show how the Bouligand-type (twisted plywood) arrangement of collagen fibril lamellae has a key role in developing their unique protective properties, by using in situ synchrotron small-angle X-ray scattering during mechanical tensile tests to observe deformation mechanisms in the fibrils. Specifically, the Bouligand-type structure allows the lamellae to reorient in response to the loading environment remarkably, most lamellae reorient towards the tensile axis and deform in tension through stretching/sliding mechanisms, whereas other lamellae sympathetically rotate away from the tensile axis and compress, thereby enhancing the scale's ductility and toughness to prevent fracture.
Fracture toughness of ultra-high molecular weight polyethylene: A basis for defining the crack-initiation toughness in polymers
Publisher: Elsevier BV
Date: 2019
Protective role of Arapaima gigas fish scales: Structure and mechanical behavior
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.ACTBIO.2014.04.009
Abstract: The scales of the arapaima (Arapaima gigas), one of the largest freshwater fish in the world, can serve as inspiration for the design of flexible dermal armor. Each scale is composed of two layers: a laminate composite of parallel collagen fibrils and a hard, highly mineralized surface layer. We review the structure of the arapaima scales and examine the functions of the different layers, focusing on the mechanical behavior, including tension and penetration of the scales, with and without the highly mineralized outer layer. We show that the fracture of the mineral and the stretching, rotation and delamination of collagen fibrils dissipate a significant amount of energy prior to catastrophic failure, providing high toughness and resistance to penetration by predator teeth. We show that the arapaima's scale has evolved to minimize damage from penetration by predator teeth through a Bouligand-like arrangement of successive layers, each consisting of parallel collagen fibrils with different orientations. This inhibits crack propagation and restricts damage to an area adjoining the penetration. The flexibility of the lamellae is instrumental to the redistribution of the compressive stresses in the underlying tissue, decreasing the severity of the concentrated load produced by the action of a tooth. The experimental results, combined with small-angle X-ray scattering characterization and molecular dynamics simulations, provide a complete picture of the mechanisms of deformation, delamination and rotation of the lamellae during tensile extension of the scale.
Enhanced fatigue endurance of metallic glasses through a staircase-like fracture mechanism
Publisher: Proceedings of the National Academy of Sciences
Date: 28-10-2013
Abstract: We believe this article is of broad interest to the materials science and engineering community. Bulk-metallic glasses (BMGs) are currently considered candidate materials for numerous structural applications. A major limitation in their use as engineering material is the often poor and inconsistent fatigue behavior. Although recently developed BMG composites provide one solution to this problem, fatigue remains a main issue for monolithic metallic glasses. The authors report unexpectedly high fatigue resistance in a monolithic Pd-based glass arising from extensive shear-band plasticity, resulting in a very rough and periodic “staircase” crack trajectory. The research both reveals a unique mechanism in fatigue of a monolithic metallic glass and demonstrates that this mechanism mitigates previous limitations on its use as an engineering material.
Modifications to Nano‐ and Microstructural Quality and the Effects on Mechanical Integrity in Paget's Disease of Bone
Publisher: Wiley
Date: 22-01-2015
DOI: 10.1002/JBMR.2340
Abstract: Paget's disease of bone (PDB) is the second most common bone disease mostly developing after 50 years of age at one or more localized skeletal sites it is associated with severely high bone turnover, bone enlargement, bowing/deformity, cracking, and pain. Here, to specifically address the origins of the deteriorated mechanical integrity, we use a cohort of control and PDB human biopsies to investigate multiscale architectural and compositional modifications to the bone structure (ie, bone quality) and relate these changes to mechanical property measurements to provide further insight into the clinical manifestations (ie, deformities and bowing) and fracture risk caused by PDB. Here, at the level of the collagen and mineral (ie, nanometer-length scale), we find a 19% lower mineral content and lower carbonate-to-phosphate ratio in PDB, which accounts for the 14% lower stiffness and 19% lower hardness promoting plastic deformation in pathological bone. At the microstructural scale, trabecular regions are known to become densified, whereas cortical bone loses its characteristic parallel-aligned osteonal pattern, which is replaced with a mosaic of lamellar and woven bone. Although we find this loss of anisotropic alignment produces a straighter crack path in mechanically-loaded PDB cases, cortical fracture toughness appears to be maintained due to increased plastic deformation. Clearly, the altered quality of the bone structure in PDB affects the mechanical integrity leading to complications such as bowing, deformities, and stable cracks called fissure fractures associated with this disease. Although the lower mineralization and loss of aligned Haversian structures do produce a lower modulus tissue, which is susceptible to deformities, our results indicate that the higher levels of plasticity may compensate for the lost microstructural features and maintain the resistance to crack growth.
A study of size effects in bioinspired, “nacre-like”, metal-compliant-phase (nickel-alumina) coextruded ceramics
Publisher: Elsevier BV
Date: 04-2018
Contributions of Material Properties and Structure to Increased Bone Fragility for a Given Bone Mass in the UCD‐T2DM Rat Model of Type 2 Diabetes
Publisher: Wiley
Date: 22-02-2018
DOI: 10.1002/JBMR.3393
On the understanding of the effects of sample size on the variability in fracture toughness of bulk metallic glasses
Publisher: Elsevier BV
Date: 03-2017
Nacre toughening due to cooperative plastic deformation of stacks of co-oriented aragonite platelets
Publisher: Springer Science and Business Media LLC
Date: 28-10-2020
DOI: 10.1038/S43246-020-00078-Y
Abstract: Nacre’s structure-property relationships have been a source of inspiration for designing advanced functional materials with both high strength and toughness. These outstanding mechanical properties have been mostly attributed to the interplay between aragonite platelets and organic matrices in the typical brick-and-mortar structure. Here, we show that crystallographically co-oriented stacks of aragonite platelets, in both columnar and sheet nacre, define another hierarchical level that contributes to the toughening of nacre. By correlating piezo-Raman and micro-indentation results, we quantify the residual strain energy associated with strain hardening capacity. Our findings suggest that the aragonite stacks, with characteristic dimensions of around 20 µm, effectively store energy through cooperative plastic deformation. The existence of a larger length scale beyond the brick-and-mortar structure offers an opportunity for a more efficient implementation of biomimetic design.
Nanoscale origins of the damage tolerance of the high-entropy alloy CrMnFeCoNi
Publisher: Springer Science and Business Media LLC
Date: 09-12-2015
DOI: 10.1038/NCOMMS10143
Abstract: Damage tolerance can be an elusive characteristic of structural materials requiring both high strength and ductility, properties that are often mutually exclusive. High-entropy alloys are of interest in this regard. Specifically, the single-phase CrMnFeCoNi alloy displays tensile strength levels of ∼1 GPa, excellent ductility (∼60–70%) and exceptional fracture toughness ( K JIc MPa√m). Here through the use of in situ straining in an aberration-corrected transmission electron microscope, we report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.
Medium-range order dictates local hardness in bulk metallic glasses
Publisher: Elsevier BV
Date: 04-2021
Effect of temperature on the fatigue-crack growth behavior of the high-entropy alloy CrMnFeCoNi
Publisher: Elsevier BV
Date: 09-2017
Nanocomposites of Titanium Dioxide and Polystyrene-Poly(ethylene oxide) Block Copolymer as Solid-State Electrolytes for Lithium Metal Batteries
Publisher: The Electrochemical Society
Date: 2013
DOI: 10.1149/2.117309JES
Technical parameters affecting grain refinement by high pressure torsion
Publisher: Walter de Gruyter GmbH
Date: 12-2009
DOI: 10.3139/146.110224
Abstract: High pressure torsion is a well known and widespread processing technique for severe plastic deformation. The aim of high pressure torsion and other comparable techniques is to obtain ultrafine-grained or even nanocrystalline materials with enhanced mechanical and physical properties compared with their coarse-grained counterparts. Generally this refinement process is strongly influenced by processing parameters such as temperature or accumulated strain, but can also simply be affected by the entire experimental setup. Therefore, the benefits and limitations of the process with regard to grain refinement, homogeneity and specimen size, underlined with experimental results using different tools, will be discussed.
On the tear resistance of skin
Publisher: Springer Science and Business Media LLC
Date: 27-03-2015
DOI: 10.1038/NCOMMS7649
Abstract: Tear resistance is of vital importance in the various functions of skin, especially protection from predatorial attack. Here, we mechanistically quantify the extreme tear resistance of skin and identify the underlying structural features, which lead to its sophisticated failure mechanisms. We explain why it is virtually impossible to propagate a tear in rabbit skin, chosen as a model material for the dermis of vertebrates. We express the deformation in terms of four mechanisms of collagen fibril activity in skin under tensile loading that virtually eliminate the possibility of tearing in pre-notched s les: fibril straightening, fibril reorientation towards the tensile direction, elastic stretching and interfibrillar sliding, all of which contribute to the redistribution of the stresses at the notch tip.
Impact of test environment on the fracture resistance of cortical bone
Publisher: Elsevier BV
Date: 05-2022
DOI: 10.1016/J.JMBBM.2022.105155
Abstract: Water is a crucial component of bone, affecting the interplay of collagen and minerals and contributing to bone's high strength and ductility. Dehydration has been shown to significantly effect osseous mechanical properties however, studies comparing the effects of various dehydrating environments on fracture toughness of bone are scarce. Accordingly, the crack resistance curve (R-curve) behavior of human and sheep cortical bone was characterized in a bio-bath, in ambient pressure air, and in scanning electron microscopes (SEMs) under three different environmental conditions (water vapor pressure, air pressure, and high-vacuum). The aim of this work was to better understand the impact of test environment on both intrinsic and extrinsic toughening and hence crack initiation toughness, K
Exceptional fracture toughness of CrCoNi-based medium- and high-entropy alloys at 20 kelvin.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-12-2022
Abstract: CrCoNi-based medium- and high-entropy alloys display outstanding damage tolerance, especially at cryogenic temperatures. In this study, we examined the fracture toughness values of the equiatomic CrCoNi and CrMnFeCoNi alloys at 20 kelvin (K). We found exceptionally high crack-initiation fracture toughnesses of 262 and 459 megapascal-meters
Machine-learning assisted laser powder bed fusion process optimization for AlSi10Mg: New microstructure description indices and fracture mechanisms
Publisher: Elsevier BV
Date: 12-2020
Exceptional damage-tolerance of a medium-entropy alloy CrCoNi at cryogenic temperatures
Publisher: Springer Science and Business Media LLC
Date: 02-02-2016
DOI: 10.1038/NCOMMS10602
Abstract: High-entropy alloys are an intriguing new class of metallic materials that derive their properties from being multi-element systems that can crystallize as a single phase, despite containing high concentrations of five or more elements with different crystal structures. Here we examine an equiatomic medium-entropy alloy containing only three elements, CrCoNi, as a single-phase face-centred cubic solid solution, which displays strength-toughness properties that exceed those of all high-entropy alloys and most multi-phase alloys. At room temperature, the alloy shows tensile strengths of almost 1 GPa, failure strains of ∼70% and K JIc fracture-toughness values above 200 MPa m 1/2 at cryogenic temperatures strength, ductility and toughness of the CrCoNi alloy improve to strength levels above 1.3 GPa, failure strains up to 90% and K JIc values of 275 MPa m 1/2 . Such properties appear to result from continuous steady strain hardening, which acts to suppress plastic instability, resulting from pronounced dislocation activity and deformation-induced nano-twinning.
The role of collagen in the dermal armor of the boxfish
Publisher: Elsevier BV
Date: 11-2020
Damage tolerance of nuclear graphite at elevated temperatures
Publisher: Springer Science and Business Media LLC
Date: 30-06-2017
DOI: 10.1038/NCOMMS15942
Abstract: Nuclear-grade graphite is a critically important high-temperature structural material for current and potentially next generation of fission reactors worldwide. It is imperative to understand its damage-tolerant behaviour and to discern the mechanisms of damage evolution under in-service conditions. Here we perform in situ mechanical testing with synchrotron X-ray computed micro-tomography at temperatures between ambient and 1,000 °C on a nuclear-grade Gilsocarbon graphite. We find that both the strength and fracture toughness of this graphite are improved at elevated temperature. Whereas this behaviour is consistent with observations of the closure of microcracks formed parallel to the covalent- sp 2 -bonded graphene layers at higher temperatures, which accommodate the more than tenfold larger thermal expansion perpendicular to these layers, we attribute the elevation in strength and toughness primarily to changes in the residual stress state at 800–1,000 °C, specifically to the reduction in significant levels of residual tensile stresses in the graphite that are ‘frozen-in’ following processing.
Review on the EFDA programme on tungsten materials technology and science
Publisher: Elsevier BV
Date: 10-2011
High temperature x-ray micro-tomography
Publisher: Author(s)
Date: 2016
DOI: 10.1063/1.4952925
Fracture behaviour of tungsten–vanadium and tungsten–tantalum alloys and composites
Publisher: Elsevier BV
Date: 06-2011
Fracture resistance of AlSi10Mg fabricated by laser powder bed fusion
Publisher: Elsevier BV
Date: 06-2021
Natural Flexible Dermal Armor
Publisher: Wiley
Date: 15-11-2012
Abstract: Fish, reptiles, and mammals can possess flexible dermal armor for protection. Here we seek to find the means by which Nature derives its protection by examining the scales from several fish (Atractosteus spatula, Arapaima gigas, Polypterus senegalus, Morone saxatilis, Cyprinius carpio), and osteoderms from armadillos, alligators, and leatherback turtles. Dermal armor has clearly been developed by convergent evolution in these different species. In general, it has a hierarchical structure with collagen fibers joining more rigid units (scales or osteoderms), thereby increasing flexibility without significantly sacrificing strength, in contrast to rigid monolithic mineral composites. These dermal structures are also multifunctional, with hydrodynamic drag (in fish), coloration for camouflage or intraspecies recognition, temperature and fluid regulation being other important functions. The understanding of such flexible dermal armor is important as it may provide a basis for new synthetic, yet bioinspired, armor materials.
Osteocyte-Intrinsic TGF-β Signaling Regulates Bone Quality through Perilacunar/Canalicular Remodeling
Publisher: Elsevier BV
Date: 11-2017
Atypical fracture with long-term bisphosphonate therapy is associated with altered cortical composition and reduced fracture resistance
Publisher: Proceedings of the National Academy of Sciences
Date: 31-07-2017
Abstract: Since the first reports of atypical femoral fractures (AFFs), a clinical phenomenon in which patients experience catastrophic brittle fractures of the femoral shaft with minimal trauma, the risk associated with bisphosphonates, the most widely prescribed pharmaceuticals for osteoporosis, has become increasingly well-established. However, the underlying cause of AFFs and their causal relationship to bisphosphonates is unknown. Here we examine bone tissue from women with AFFs and show that long-term bisphosphonate treatment degrades the fracture-resistance toughening mechanisms that are inherent to healthy bone. Our work resolves the apparent paradox of AFFs as a side effect of the most common osteoporosis treatment by clarifying the differing effects of bisphosphonates on bone tissue structure and mechanical properties across multiple length scales.
Electrically reversible cracks in an intermetallic film controlled by an electric field
Publisher: Springer Science and Business Media LLC
Date: 03-01-2018
DOI: 10.1038/S41467-017-02454-8
Abstract: Cracks in solid-state materials are typically irreversible. Here we report electrically reversible opening and closing of nanoscale cracks in an intermetallic thin film grown on a ferroelectric substrate driven by a small electric field (~0.83 kV/cm). Accordingly, a nonvolatile colossal electroresistance on–off ratio of more than 10 8 is measured across the cracks in the intermetallic film at room temperature. Cracks are easily formed with low-frequency voltage cycling and remain stable when the device is operated at high frequency, which offers intriguing potential for next-generation high-frequency memory applications. Moreover, endurance testing demonstrates that the opening and closing of such cracks can reach over 10 7 cycles under 10-μs pulses, without catastrophic failure of the film.
Bioinspired Hydroxyapatite/Poly(methyl methacrylate) Composite with a Nacre‐Mimetic Architecture by a Bidirectional Freezing Method
Publisher: Wiley
Date: 10-11-2015
Abstract: Using a bidirectional freezing technique, combined with uniaxial pressing and in situ polymerization, "nacre-mimetic" hydroxyapatite oly(methyl methacrylate) (PMMA) composites are developed by processing large-scale aligned lamellar ceramic scaffolds. Structural and mechanical characterization shows "brick-and-mortar" structures, akin to nacre, with interesting combinations of strength, stiffness, and work of fracture, which provide a pathway to making strong and tough lightweight materials.
Bioinspired nacre-like alumina with a bulk-metallic glass-forming alloy as a compliant phase
Publisher: Springer Science and Business Media LLC
Date: 27-02-2019
DOI: 10.1038/S41467-019-08753-6
Abstract: Bioinspired ceramics with micron-scale ceramic “bricks” bonded by a metallic “mortar” are projected to result in higher strength and toughness ceramics, but their processing is challenging as metals do not typically wet ceramics. To resolve this issue, we made alumina structures using rapid pressureless infiltration of a zirconium-based bulk-metallic glass mortar that reactively wets the surface of freeze-cast alumina preforms. The mechanical properties of the resulting Al 2 O 3 with a glass-forming compliant-phase change with infiltration temperature and ceramic content, leading to a trade-off between flexural strength (varying from 89 to 800 MPa) and fracture toughness (varying from 4 to more than 9 MPa·m ½ ). The high toughness levels are attributed to brick pull-out and crack deflection along the ceramic/metal interfaces. Since these mechanisms are enabled by interfacial failure rather than failure within the metallic mortar, the potential for optimizing these bioinspired materials for damage tolerance has still not been fully realized.
Notch fatigue of ultrahigh molecular weight polyethylene (UHMWPE) used in total joint replacements
Publisher: Elsevier BV
Date: 07-2016
DOI: 10.1016/J.JMBBM.2016.02.014
Abstract: Ultrahigh molecular weight polyethylene (UHMWPE) has remained the primary polymer used in hip, knee and shoulder replacements for over 50 years. Recent case studies have demonstrated that catastrophic fatigue fracture of the polymer can severely limit device lifetime and are often associated with stress concentration (notches) integrated into the design. This study evaluates the influence of notch geometry on the fatigue of three formulations of UHMWPE that are in use today. A linear-elastic fracture mechanics approach is adopted to evaluate crack propagation as a function of notch root radius, heat treatment and Vitamin E additions. Specifically, a modified stress-intensity factor that accounts for notch geometry was utilized to model the crack driving force. The degree of notch plasticity for each material/notch combination was further evaluated using finite element methods. Experimental evaluation of crack speed as a function of stress intensity was conducted under cyclic tensile loading, taking crack length and notch plasticity into consideration. Results demonstrated that crack propagation in UHMWPE emanating from a notch was primarily affected by microstructural influences (cross-linking) rather than differences in notch geometry.
Deformation-induced medium-range order changes in bulk metallic glasses
Publisher: American Physical Society (APS)
Date: 25-04-2022
Structure and fracture resistance of alligator gar (Atractosteus spatula) armored fish scales
Publisher: Elsevier BV
Date: 04-2013
DOI: 10.1016/J.ACTBIO.2012.12.026
Abstract: The alligator gar is a large fish with flexible armor consisting of ganoid scales. These scales contain a thin layer of ganoine (microhardness ~2.5 GPa) and a bony body (microhardness ~400 MPa), with jagged edges that provide effective protection against predators. We describe here the structure of both ganoine and bony foundation and characterize the mechanical properties and fracture mechanisms. The bony foundation is characterized by two components: a mineralized matrix and parallel arrays of tubules, most of which contain collagen fibers. The spacing of the empty tubules is ~60 μm the spacing of those filled with collagen fibers is ~7 μm. Using micromechanical testing of such scales in a variable-pressure scanning electron microscope, we identify interactions between propagating cracks and the microstructure, and show that the toughness of the scales increases with crack extension in a classical resistance-curve response from the activation of extrinsic toughening mechanisms. We demonstrate how mechanical damage evolves in these structures, and further identify that the reinforcement of the mineral by the network of collagen fibers is the principal toughening mechanism resisting such damage. Additionally, we define the anisotropy of the toughness of the scales and relate this to the collagen fiber orientation.
Strength and fracture resistance of in-situ alloyed compositionally-graded Al-Si processed by dual-wire arc directed energy deposition
Publisher: Elsevier BV
Date: 12-2022
Design considerations for high entropy alloys in advanced nuclear applications
Publisher: Elsevier BV
Date: 08-2022
Increasing M2(dobdc) Loading in Selective Mixed-Matrix Membranes: A Rubber Toughening Approach
Publisher: American Chemical Society (ACS)
Date: 30-01-2018
Processing, Microstructure and Mechanical Properties of the CrMnFeCoNi High-Entropy Alloy
Publisher: Springer Science and Business Media LLC
Date: 19-08-2015
Real-time nanoscale observation of deformation mechanisms in CrCoNi-based medium- to high-entropy alloys at cryogenic temperatures
Publisher: Elsevier BV
Date: 05-2019
Anisotropic fracture resistance of avian eggshell
Publisher: Elsevier BV
Date: 10-2020
Mechanical Competence and Bone Quality Develop During Skeletal Growth
Publisher: Wiley
Date: 17-06-2019
DOI: 10.1002/JBMR.3730
Abstract: Bone fracture risk is influenced by bone quality, which encompasses bone's composition as well as its multiscale organization and architecture. Aging and disease deteriorate bone quality, leading to reduced mechanical properties and higher fracture incidence. Largely unexplored is how bone quality and mechanical competence progress during longitudinal bone growth. Human femoral cortical bone was acquired from fetal (n = 1), infantile (n = 3), and 2- to 14-year-old cases (n = 4) at the mid-diaphysis. Bone quality was assessed in terms of bone structure, osteocyte characteristics, mineralization, and collagen orientation. The mechanical properties were investigated by measuring tensile deformation at multiple length scales via synchrotron X-ray diffraction. We find dramatic differences in mechanical resistance with age. Specifically, cortical bone in 2- to 14-year-old cases exhibits a 160% greater stiffness and 83% higher strength than fetal/infantile cases. The higher mechanical resistance of the 2- to 14-year-old cases is associated with advantageous bone quality, specifically higher bone volume fraction, better micronscale organization (woven versus lamellar), and higher mean mineralization compared with fetal/infantile cases. Our study reveals that bone quality is superior after remodeling/modeling processes convert the primary woven bone structure to lamellar bone. In this cohort of female children, the microstructural differences at the femoral diaphysis were apparent between the 1- to 2-year-old cases. Indeed, the lamellar bone in 2- to 14-year-old cases had a superior structural organization (collagen and osteocyte characteristics) and composition for resisting deformation and fracture than fetal/infantile bone. Mechanistically, the changes in bone quality during longitudinal bone growth lead to higher fracture resistance because collagen fibrils are better aligned to resist tensile forces, while elevated mean mineralization reinforces the collagen scaffold. Thus, our results reveal inherent weaknesses of the fetal/infantile skeleton signifying its inferior bone quality. These results have implications for pediatric fracture risk, as bone produced at ossification centers during children's longitudinal bone growth could display similarly weak points. © 2019 American Society for Bone and Mineral Research.
An in situ ambient and cryogenic transmission electron microscopy study of the effects of temperature on dislocation behavior in CrCoNi-based high-entropy alloys with low stacking-fault energy
Publisher: AIP Publishing
Date: 27-12-2021
DOI: 10.1063/5.0069086
Abstract: Temperature is known to affect deformation mechanisms in metallic alloys. As temperature decreases, the stacking-fault energy in many face-centered cubic (fcc) alloys decreases, resulting in a change of deformation mode from dislocation slip to deformation twinning. Such an impact of temperature can be more complex in compositionally heterogeneous microstructures that exhibit, for ex le, local concentration fluctuation such as that in multi-principal element alloys. In this work, we compare the dislocation behavior and mechanical properties of a fcc Cr20Mn10Fe30Co30Ni10 high-entropy alloy at ambient and liquid-nitrogen temperatures. We find that a network of stacking faults is formed by uniformly extended dislocations at ambient temperatures with low stacking-fault energy, whereas at lower temperatures, uneven dissociation of dislocations becomes significant, which results in severe dislocation pile-ups together with their pronounced entanglement. Our findings indicate that as the stacking-fault energy decreases with decreasing temperature, the heterogeneity of the distribution of elements becomes more dominant in tuning the local variation of lattice resistance. As a result, the change in dislocation behavior at low temperatures strongly affects microstructural evolution and consequently leads to significantly more pronounced work hardening.
Role of pre-existing shear band morphology in controlling the fracture behavior of a Zr–Ti–Cu–Ni–Al bulk metallic glass
Publisher: Elsevier BV
Date: 06-2020
On the development of ice-templated silicon carbide scaffolds for nature-inspired structural materials
Publisher: Elsevier BV
Date: 10-2013
Erratum: Size-dependent fracture toughness of bulk metallic glasses (Acta Materialia (2014) 70 (198-207))
Publisher: Elsevier BV
Date: 11-2014
Fracture resistance of human cortical bone across multiple length-scales at physiological strain rates
Publisher: Elsevier BV
Date: 07-2014
DOI: 10.1016/J.BIOMATERIALS.2014.03.066
Abstract: While most fracture-mechanics investigations on bone have been performed at low strain rates, physiological fractures invariably occur at higher loading rates. Here, at strain rates from 10(-5) to 10(-1) s(-1), we investigate deformation and fracture in bone at small length-scales using in situ small-angle x-ray scattering (SAXS) to study deformation in the mineralized collagen fibrils and at the microstructural level via fracture-mechanics experiments to study toughening mechanisms generating toughness through crack-tip shielding. Our results show diminished bone toughness at increasing strain rates as cracks penetrate through the osteons at higher strain rates instead of deflecting at the cement lines, which is a prime toughening mechanism in bone at low strain rates. The absence of crack deflection mechanisms at higher strain rates is consistent with lower intrinsic bone matrix toughness. In the SAXS experiments, higher fibrillar strains at higher strain rates suggest less inelastic deformation and thus support a lower intrinsic toughness. The increased incidence of fracture induced by high strain rates can be associated with a loss in toughness in the matrix caused by a strain rate induced stiffening of the fibril ductility, i.e., a "locking-up" of the viscous sliding and sacrificial bonding mechanisms, which are the origin of inelastic deformation (and toughness) in bone at small length-scales.
Size-dependent fracture toughness of bulk metallic glasses
Publisher: Elsevier BV
Date: 05-2014
Multiscale structure and damage tolerance of coconut shells
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.JMBBM.2017.05.024
Abstract: We investigated the endocarp of the fruit of Cocos nucifera (i.e., the inner coconut shell), examining the structure across multiple length scales through advanced characterization techniques and in situ testing of mechanical properties. Like many biological materials, the coconut shell possesses a hierarchical structure with distinct features at different length scales that depend on orientation and age. Aged coconut was found to have a significantly stronger (ultimate tensile strength, UTS = 48.5MPa), stiffer (Young's modulus, E = 1.92GPa), and tougher (fracture resistance (R-curve) peak of K
Correction to Tetrapod Nanocrystals as Fluorescent Stress Probes of Electrospun Nanocomposites
Publisher: American Chemical Society (ACS)
Date: 14-10-2013
DOI: 10.1021/NL4035785
Synchrotron X-ray micro-tomography at the Advanced Light Source: Developments in high-temperature in-situ mechanical testing
Publisher: IOP Publishing
Date: 06-2017
On the Room-Temperature Mechanical Properties of an Ion-Irradiated TiZrNbHfTa Refractory High Entropy Alloy
Publisher: Springer Science and Business Media LLC
Date: 04-11-2019
A Highly Fatigue-Resistant Zr-Based Bulk Metallic Glass
Publisher: Springer Science and Business Media LLC
Date: 13-08-2013
Effect of heat treatment on the strength and fracture resistance of a laser powder bed fusion-processed 18Ni-300 maraging steel
Publisher: Elsevier BV
Date: 06-2022
Atom Probe Analysis of a Zr-based Bulk Metallic Glass
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621012824
Abstract: Zr-based bulk metallic glasses (BMGs) are amorphous alloys that can exhibit excellent mechanical properties, including high yield strength and fracture toughness. These properties are linked to local microstructural heterogeneities. Whether via microscopy-based techniques, synchrotron techniques, or calorimetric approaches, the amorphous structure of BMGs makes the characterisation of the details of these local structural and chemical heterogeneities extremely challenging. Our focus here is on atom probe tomography (APT), where considerable uncertainty remains in terms of how and when to apply this otherwise powerful technique to amorphous materials. This work reports a systematic evaluation of the experimental parameter space. We report results of BMG composition acquired against various APT operating parameters for Zr63.96Cu13.36Ni10.29Al11.04Nb1.25 (at. %). We demonstrate that a customised peak-based ranging approach yields satisfactory compositional accuracy with absolute errors of & at. %. Beyond composition, we have discussed the data quality in terms of attributes of the mass spectra: mass resolution, signal-to-thermal tail ratio, and overlapped peak ratio. We also assess the composition of the well-known clustered evaporation effects, common in APT data of BMGs. We conclude that these regions have negligible differences in composition from the surrounding “matrix” or bulk in these alloys.
On the Origins of Fracture Toughness in Advanced Teleosts: How the Swordfish Sword's Bone Structure and Composition Allow for Slashing under Water to Kill or Stun Prey
Publisher: Wiley
Date: 02-05-2019
On the Fracture Behavior of Bulk Metallic Glasses
Publisher: Springer International Publishing
Date: 27-05-2018
Temperature and load-ratio dependent fatigue-crack growth in the CrMnFeCoNi high-entropy alloy
Publisher: Elsevier BV
Date: 07-2019
High temperature fracture experiments on tungsten–rhenium alloys
Publisher: Elsevier BV
Date: 11-2010
Fracture toughness of graphene/aluminum nanolaminated composites
Publisher: Elsevier BV
Date: 04-2023
Fracture toughness of polycrystalline tungsten alloys
Publisher: Elsevier BV
Date: 11-2010
Intrinsic mechanical behavior of femoral cortical bone in young, osteoporotic and bisphosphonate-treated individuals in low- and high energy fracture conditions
Publisher: Springer Science and Business Media LLC
Date: 16-02-2016
DOI: 10.1038/SREP21072
Abstract: Bisphosphonates are a common treatment to reduce osteoporotic fractures. This treatment induces osseous structural and compositional changes accompanied by positive effects on osteoblasts and osteocytes. Here, we test the hypothesis that restored osseous cell behavior, which resembles characteristics of younger, healthy cortical bone, leads to improved bone quality. Microarchitecture and mechanical properties of young, treatment-naïve osteoporosis and bisphosphonate-treated cases were investigated in femoral cortices. Tissue strength was measured using three-point bending. Collagen fibril-level deformation was assessed in non-traumatic and traumatic fracture states using synchrotron small-angle x-ray scattering (SAXS) at low and high strain rates. The lower modulus, strength and fibril deformation measured at low strain rates reflects susceptibility for osteoporotic low-energy fragility fractures. Independent of age, disease and treatment status, SAXS revealed reduced fibril plasticity at high strain rates, characteristic of traumatic fracture. The significantly reduced mechanical integrity in osteoporosis may originate from porosity and alterations to the intra/extrafibrillar structure, while the fibril deformation under treatment indicates improved nano-scale characteristics. In conclusion, losses in strength and fibril deformation at low strain rates correlate with the occurrence of fragility fractures in osteoporosis, while improvements in structural and mechanical properties following bisphosphonate treatment may foster resistance to fracture during physiological strain rates.
A fracture-resistant high-entropy alloy for cryogenic applications
Publisher: American Association for the Advancement of Science (AAAS)
Date: 05-09-2014
Abstract: Metal alloys normally consist of one dominant element, with others in small amounts to improve specific properties. For ex le, stainless steel is primarily iron with nickel and chromium but may contain trace amounts of other elements. Gludovatz et al. explored the properties of a high-entropy alloy made from equal amounts of chromium, manganese, iron, cobalt, and nickel. Not only does this alloy show excellent strength, ductility, and toughness, but these properties improve at cryogenic temperatures where most alloys change from ductile to brittle. Science , this issue p. 1153
Fracture properties of high-entropy alloys
Publisher: Springer Science and Business Media LLC
Date: 02-2022
DOI: 10.1557/S43577-022-00267-9
Abstract: Since the concept of high-entropy alloys (HEAs) as materials with at least four or five principal elements in (near)-equiatomic composition was introduced in 2004, this new class of materials has penetrated essentially all materials science-related fields. The main reason for this is that some face-centered-cubic alloy compositions have been shown to exhibit truly outstanding mechanical properties with extraordinary combinations of strength, ductility, and fracture toughness, particularly at cryogenic temperatures, whereas certain body-centered-cubic refractory compositions display remarkable high-temperature strength. While significant efforts have been put into rapid screening and narrowing the compositional space of HEAs to a manageable scope, there are still only a few metallic alloys that push the limits of mechanical performance. Here, we review work on some of the most damage-tolerant HEAs discovered to date and discuss the fundamental reasons why their resistance to fracture and subsequent stable crack growth is so exceptional. Graphical abstract
High-temperature damage-tolerance of coextruded, bioinspired (“nacre-like”), alumina/nickel compliant-phase ceramics
Publisher: Elsevier BV
Date: 2019
Alendronate treatment alters bone tissues at multiple structural levels in healthy canine cortical bone
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.BONE.2015.08.002
Abstract: Bisphosphonates are widely used to treat osteoporosis, but have been associated with atypical femoral fractures (AFFs) in the long term, which raises a critical health problem for the aging population. Several clinical studies have suggested that the occurrence of AFFs may be related to the bisphosphonate-induced changes of bone turnover, but large discrepancies in the results of these studies indicate that the salient mechanisms responsible for any loss in fracture resistance are still unclear. Here the role of bisphosphonates is examined in terms of the potential deterioration in fracture resistance resulting from both intrinsic (plasticity) and extrinsic (shielding) toughening mechanisms, which operate over a wide range of length-scales. Specifically, we compare the mechanical properties of two groups of humeri from healthy beagles, one control group comprising eight females (oral doses of saline vehicle, 1 mL/kg/day, 3 years) and one treated group comprising nine females (oral doses of alendronate used to treat osteoporosis, 0.2mg/kg/day, 3 years). Our data demonstrate treatment-specific reorganization of bone tissue identified at multiple length-scales mainly through advanced synchrotron x-ray experiments. We confirm that bisphosphonate treatments can increase non-enzymatic collagen cross-linking at molecular scales, which critically restricts plasticity associated with fibrillar sliding, and hence intrinsic toughening, at nanoscales. We also observe changes in the intracortical architecture of treated bone at microscales, with partial filling of the Haversian canals and reduction of osteon number. We hypothesize that the reduced plasticity associated with BP treatments may induce an increase in microcrack accumulation and growth under cyclic daily loadings, and potentially increase the susceptibility of cortical bone to atypical (fatigue-like) fractures.
On the onset of deformation twinning in the CrFeMnCoNi high-entropy alloy using a novel tensile specimen geometry
Publisher: Elsevier BV
Date: 07-2019
Developing strength and toughness in bio-inspired silicon carbide hybrid materials containing a compliant phase
Publisher: Elsevier BV
Date: 10-2015
Real-time observations of TRIP-induced ultrahigh strain hardening in a dual-phase CrMnFeCoNi high-entropy alloy
Publisher: Springer Science and Business Media LLC
Date: 11-02-2020
DOI: 10.1038/S41467-020-14641-1
Abstract: Strategies involving metastable phases have been the basis of the design of numerous alloys, yet research on metastable high-entropy alloys is still in its infancy. In dual-phase high-entropy alloys, the combination of local chemical environments and loading-induced crystal structure changes suggests a relationship between deformation mechanisms and chemical atomic distribution, which we examine in here in a Cantor-like Cr 20 Mn 6 Fe 34 Co 34 Ni 6 alloy, comprising both face-centered cubic ( fcc ) and hexagonal closed packed ( hcp ) phases. We observe that partial dislocation activities result in stable three-dimensional stacking-fault networks. Additionally, the fraction of the stronger hcp phase progressively increases during plastic deformation by forming at the stacking-fault network boundaries in the fcc phase, serving as the major source of strain hardening. In this context, variations in local chemical composition promote a high density of Lomer-Cottrell locks, which facilitate the construction of the stacking-fault networks to provide nucleation sites for the hcp phase transformation.
Compositional variations in equiatomic CrMnFeCoNi high-entropy alloys
Publisher: Elsevier BV
Date: 10-2021
A Novel Approach to Developing Biomimetic (“Nacre‐Like”) Metal‐Compliant‐Phase (Nickel–Alumina) Ceramics through Coextrusion
Publisher: Wiley
Date: 30-09-2016
Abstract: Bioinspired "brick-and-mortar" alumina ceramics containing a nickel compliant phase are synthesized by coextrusion of alumina and nickel oxide. Results show that these structures are coarser yet exhibit exceptional resistance-curve behavior with a fracture toughness three or more times higher than that of alumina, consistent with significant extrinsic toughening, from crack bridging and "brick" pull-out, in the image of natural nacre.
Dislocation mechanisms and 3D twin architectures generate exceptional strength-ductility-toughness combination in CrCoNi medium-entropy alloy
Publisher: Springer Science and Business Media LLC
Date: 20-02-2017
DOI: 10.1038/NCOMMS14390
Abstract: Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ , and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a dual function: conventional twin-boundary (TB) strengthening from blockage of dislocations impinging on TBs, coupled with the 3D twin network which offers pathways for dislocation glide along, and cross-slip between, intersecting TB-matrix interfaces. The stable twin architecture is not disrupted by interfacial dislocation glide, serving as a continuous source of strength, ductility and toughness.
A study into the crack propagation resistance of pure tungsten
Publisher: Elsevier BV
Date: 03-2013
Related Organisations
E O Lawrence Berkeley National Laboratory
Location: United States of America
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