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Pair distribution function (PDF) analysis is a powerful technique to understand atomic scale structure in materials science. Unlike X-ray diffraction (XRD)-based PDF analysis, the PDF calculated from electron diffraction patterns (EDPs) using transmission electron microscopy can provide structural information from specific locations with high spatial resolution. The present work describes a new software tool for both periodic and amorphous structures that addresses several practical challenges in calculating the PDF from EDPs. The key features of this program include accurate background subtraction using a nonlinear iterative peak-clipping algorithm and automatic conversion of various types of diffraction intensity profiles into a PDF without requiring external software. The present study also evaluates the effect of background subtraction and the elliptical distortion of EDPs on PDF profiles. The EDP2PDF software is offered as a reliable tool to analyse the atomic structure of crystalline and non-crystalline materials.

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

Acta materialia 253, 118968 (2023). doi:10.1016/j.actamat.2023.118968, Ni-Nb-based bulk glass-forming alloys are among the most promising amorphous metals for industrial applica- tions due to their incomparable combination of strength, hardness, elasticity and plasticity. However, the main drawback is the limited glass-forming ability, narrowing the field of application to solely small components. In this study, we show that minor additions of P to the binary Ni-Nb system increase the glass-forming ability by 150 % to a record value of 5 mm. P can be easily added by using an industrial Ni-P pre-alloy which is readily available. The partial substitution of Nb by Ta further boosts the glass-forming ability to values 200 % higher than that of the binary base alloy. Besides conventional X-ray diffraction measurements, the amorphous nature of the samples is verified by high-energy synchrotron X-ray diffraction experiments. Moreover, the mechanical properties of the new alloy compositions are characterized in uniaxial compression tests and Vickers hardness measurements, showing a high engineering yield strength of 3 GPa, an extended plastic regime up to 10 % strain to failure and an increase of the hardness to a maximum value of 1000 HV5. Additionally, calorimetric mea- surements reveal that the modified alloys feature an extended supercooled liquid region up to 69 K upon heating, permitting thermoplastic micro molding of amorphous feedstock material., Published by Elsevier Science, Amsterdam [u.a.]

Multi-principal element alloys (MPEAs) have attracted rapidly growing attention from both research institutions and industry due to their unique microstructures and outstanding physical and chemical properties. However, the fabrication of MPEAs with desired microstructures and properties using conventional manufacturing techniques (e.g., casting) is still challenging. With the recent emergence of additive manufacturing (AM) techniques, the fabrication of MPEAs with locally tailorable microstructures and excellent mechanical properties has become possible. Therefore, it is of paramount importance to understand the key aspects of the AM processes that influence the microstructural features of AM fabricated MPEAs including porosity, anisotropy, and heterogeneity, as well as the corresponding impact on the properties. As such, this review will first present the state-of-the-art in existing AM techniques to process MPEAs. This is followed by a discussion of the microstructural features, mechanisms of microstructural evolution, and the mechanical properties of the AM fabricated MPEAs. Finally, the current challenges and future research directions are summarized with the aim to promote the further development and implementation of AM for processing MPEAs for future industrial applications.

The anisotropic mechanical properties of ultrasound freeze cast epoxy-ceramic composite materials were studied by measuring flexural strength and fracture resistance curves (R-curves) using both unnotched and notched three-point beam bending experiments, respectively, cut in three different orientations relative to the directional freezing axis. Three ultrasound frequencies of 0.699, 1.39 and 2.097 MHz were used in order to introduce different length scales into the microstructure, with 0 MHz used as the control samples. For all cases, the composites showed higher strength and fracture resistance when the crack plane cut across the direction of ice growth (denoted as the YX orientation). The anisotropic properties were more evident for the material produced without ultrasound (0 MHz) where the flexural strength was approximately 160% higher for the YX orientation compared to two orthogonal orientations. Most of the fracture resistance increase was found to occur within a crack extension, Δa, of ∼0.5 mm. Comparing the fracture resistance at Δa = 0.5 mm for the highly anisotropic 0 MHz samples showed that the YX orientation was approximately 86% tougher than the two orthogonal orientations. When the ultrasound operation frequencies of 0.699, 1.39 and 2.097 MHz were applied, the amount of anisotropy in the strength and fracture resistance gradually decreased as the operating frequency increased. The high strength and fracture resistance for the YX orientation was attributed to the alignment of the ceramic particles along the freeze front direction creating a barrier for crack propagation. Ultrasound modifies the material microstructure, introducing relatively dense ceramic layers perpendicular to the freezing front direction that act as an additional, orthogonal barrier to crack propagation. The addition of the denser layers acts to improve the mechanical properties in the weaker orientations and reduce the overall anisotropy.

Anticipating an increasing demand for hybrid double network (DN) hydrogels in biomedicine and biotechnology, this study evaluated the effects of each network on the mechanical and biological properties. Polyethylene glycol (PEG) (meth)acrylate hydrogels with varied monomer molecular weights and architectures (linear vs. 4-arm) were produced with and without an added ionically bonded alginate network and their mechanical properties were characterized using compression testing. The results showed that while some mechanical properties of PEG single network (SN) hydrogels decreased or changed negligibly with increasing molecular weight, the compressive modulus, strength, strain to failure, and toughness of DN hydrogels all significantly increased with increased PEG monomer molecular weight. At a fixed molecular weight (10 kDa), 4-arm PEG SN hydrogels exhibited better overall mechanical performance; however, this benefit was diminished for the corresponding DN hydrogels with comparable strength and toughness and lower strain to failure for the 4-arm case. Regardless of the PEG monomer structure, the alginate network made a relatively larger contribution to the overall DN mechanical properties when the covalent PEG network was looser with a larger mesh size (e.g., for larger monomer molecular weight and/or linear architecture) which presumably enabled more ionic crosslinking. Considering the biological performance, adipose derived stem cell cultures demonstrated monotonically increasing cell area and Yes-associated protein related mechanosensing with increasing amounts of alginate from 0 to 2 wt.%, demonstrating the possibility for using DN hydrogels in guiding musculoskeletal differentiation. These findings will be useful to design suitable hydrogels with controllable mechanical and biological properties for mechanically demanding applications. STATEMENT OF SIGNIFICANCE: Hydrogels are widely used in commercial applications, and recently developed hybrid double network hydrogels have enhanced strength and toughness that will enable further expansion into more mechanically demanding applications (e.g., medical implants, etc.). The significance of this work is that it uncovers some key principles regarding monomer molecular weight, architecture, and concentration for developing strong and tough hybrid double network hydrogels that would not be predicted from their single network counterparts or a linear combination of the two networks. Additionally, novel insight is given into the biological performance of hybrid double network hydrogels in the presence of adipose derived stem cell cultures which suggests new scope for using double network hydrogels in guiding musculoskeletal differentiation.

AlSi10Mg alloy modified with 4 wt.% cerium was fabricated by selective laser melting and subjected to a T6 solutionizing (2 h at 535°C) and ageing (10 h at 160°C) heat treatment. Microstructure, pr...

Both uniform and graded gyroid cellular structures (GCSs) of NiTi have been successfully fabricated by laser powder bed fusion (LPBF) additive manufacturing. NiTi GCSs were produced with gradients along two different directions, and the surface morphology and mechanical properties of different GCSs were systematically studied using micro-x-ray computed tomography, monotonic compression, and compression–compression fatigue testing. The results showed that all the LPBF NiTi structures exhibited similar nominal compressive elastic modulus (5–7 GPa) to human bones. By altering the density distribution of the novel GCSs, different deformation and fatigue properties were achieved. GCSs with graded density parallel to each layer (Y-GCSs) exhibited a similar shear compression failure behavior and slightly better fatigue behavior compared to the uniform structure. In contrast, GCSs with graded density parallel to the building direction (Z-GCSs) exhibited a layer-by-layer deformation and collapse behavior under compression, while the fatigue life was worse than the uniform structure.

Bulk metallic glasses (BMGs) are materials with outstanding strength and elastic properties that make them tantalizing for engineering applications, yet our poor understanding of how their amorphous atomic arrangements control their broader mechanical properties (hardness, wear, fracture, etc.) impedes our ability to apply materials science principles in their design. In this work, we uncover the hierarchical structure that exists in BMGs across the nano- to microscale by using nanobeam electron diffraction experiments. Our findings reveal that local hardness of microscale domains decreases with increasing size and volume fraction of atomic clusters with higher local medium range order (MRO). Furthermore, we propose a model of ductile phase softening that will enable the future design of BMGs by tuning the MRO size and distribution in the nanostructure.

Human tooth enamel must withstand the cyclic contact forces, wear, and corrosion processes involved with typical oral functions. Furthermore, unlike other human tissues, dental enamel does not have a significant capacity for healing or self-repair and thus the longevity of natural teeth in the oral environment depends to a large degree on the fatigue and wear properties of enamel. The purpose of this review is to provide an overview of our understanding of the fatigue and wear mechanisms of human enamel and how they relate to in vivo observations of tooth damage in the complex oral environment. A key finding of this review is that fatigue and wear processes are closely related. For example, the presence of abrasive wear particles significantly lowers the forces needed to initiate contact fatigue cracking while subsurface fatigue crack propagation drives key delamination wear mechanisms during attrition or attrition-corrosion of enamel. Furthermore, this review seeks to bring a materials science and mechanical engineering perspective to fatigue and wear phenomena. In this regard, we see developing a mechanistic description of fatigue and wear, and understanding the interconnectivity of the processes, as essential for successfully modelling enamel fatigue and wear damage and developing strategies and treatments to improve the longevity of our natural teeth. Furthermore, we anticipate that this review will stimulate ideas for extending the lifetime of the natural tooth structure and will help highlight where our understanding is too limited and where additional research into fatigue and wear of human tooth enamel is warranted.

The incorporation of mechanosensitive linkages into polymers has led to materials with dynamic force responsivity. Here we report oxanorbornadiene cross-linked double network hydrogels that release molecules through a force-mediated retro Diels-Alder reaction. The molecular design and tough double network of polyacrylamide and alginate promote significantly higher activation at substantially less force than pure polymer systems. Activation at physiologically relevant forces provides scope for instilling dynamic mechanochemical behavior in soft biological materials.

Shape-memory materials (SMMs) are characterized by their unique ability to remember and recover their shape in response to external stimuli. Over recent decades, the use of SMMs in biomedical areas such as tissue engineering, drug delivery, endovascular surgery, orthodontics, orthopedics, etc. has attracted significant attention from both academia and industry. Recently, additive manufacturing (AM) has also attracted growing interest for biomedical applications because of its ability to produce on-demand, patient-tailored devices for medical treatments. This article provides a review of current state-of-the-art AM techniques for producing SMMs for biomedical applications. First, both shape-memory alloys and shape-memory polymers are discussed regarding their fundamental characteristics and compositions, and the general principles governing their shape-memory effects. Next, current and potential biomedical applications of SMMs are presented, then available AM techniques that have been used for the fabrication of SMM-based medical devices are discussed and explored. Finally, an outlook on AM of SMMs for biomedical applications is provided.

Porous Fe3O4 scaffolds were fabricated while subject to a low (7.8 mT) magnetic field applied in helical and Bouligand motions using a custom-built tri-axial nested Helmholtz coils-based freeze-casting setup. This setup allowed for the control of a dynamic, uniform low-strength magnetic field to align particles during the freezing process, resulting in the majority of lamellar walls aligning within ± 30° of the magnetic field direction and a decrease in porosity by up to 42%. Similar to how helical and Bouligand structures in nature promote impact resistance, these magnetic field motions produced structures with improved high strain rate mechanical properties. Strain at failure was increased by up to 2 times as cracks deflected to match the applied angles of rotation of the magnetic field.

Refractory high-entropy alloys (RHEAs) are potential candidate materials for use in next-generation nuclear reactors due to their excellent mechanical performance at high temperatures. Here, we investigate the microstructure and mechanical properties of the nanocrystalline RHEA TiZrNbHfTa before and after irradiation with He2+ ions to determine radiation-induced property changes. Using nanoindentation and in situ microtensile testing we find only small changes in hardness after irradiation but a significant increase in yield and ultimate tensile strength without loss in ductility. This is associated with radiation hardening and a shift from shear localization failure with smooth fracture surfaces to a fracture morphology consisting of fine dimples and intergranular failure characteristics. Overall, the material shows excellent damage-tolerant properties with good combinations of strength and ductility both prior to and after ion irradiation.

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

Background To close elliptical excisions, surgeons commonly use the rule of halves which involves initially closing of the middle portion of the wound, followed by closure of the remaining halves. Understanding the forces required for suturing such wounds can aid excisional surgery planning to decrease complications and improve wound healing. Methods Following full thickness excision for removal of skin cancers, back wounds with 3:1 ratio of length-to-width were closed using the rule of halves. The force required to bring the wound edges into contact at the middle portion of the wound was measured, followed by the two bisected halves. Findings The average force to close the center of the wounds averaged 3.7 N and was six times larger than that of the bisected halves. The forces to close the bisected halves were consistently small, and essentially negligible ( Interpretation When planning excisional surgery to avoid complications such as tearing the dermis (cheese wiring), the use of special wound closure techniques (high tension and/or pully sutures, skin support or suture retention devices, etc.) should focus on the center suture only when using the rule of halves, as the remaining sutures require very low forces.

Objectives Understand how cooling protocols control the microstructure and mechanical properties of veneering porcelains. Methods Two porcelain powders were selected, one used to veneer metallic frameworks (VM13) and one for zirconia frameworks (VM9). After the last firing cycle, the monolithic specimens were subjected to two cooling protocols: slow and fast. Flexural strength (FS) was evaluated by three-point beam bending and fracture toughness (KIC) was evaluated by the single-edge V-notch beam (SEVNB) method. Scanning electron microscopy (SEM) was performed to determine the leucite crystal volume fraction (%), particle size, and matrix microcrack density. The results were compared by analysis of variances (ANOVA) and Tukey’s multiple comparison test. Results The mechanical properties were significantly (p Significance Controlled crystallization using slow cooling can be applied as a means of strengthening dental porcelains. However, the benefits of slow cooling may be partially offset by increasing the microcrack density in the glass matrix. To achieve the maximum benefit of slow cooling, it is recommending to develop heat treatments to produce porcelain with fine-grained and homogenously dispersed leucite crystals to achieve minimal glass matrix microcracking.

In this work, temperature dependent mechanical properties of conventional and additive manufactured Inconel 718 (IN718) after solution and aging (SA) heat treatment were measured at room temperature, 350 °C, and 650 °C. Nanoindentation technique was used to obtain material properties including hardness, reduced modulus, creep rate, creep stress exponent, and thermal activation volume. The indentation size effect (ISE) was analyzed at each temperature. The reduced modulus was measured to decrease by 26% for the conventional samples and by 22% for AM samples as temperature increases from room temperature to 650 °C. The nanoindentation hardness decreases by 19% for the conventional samples and 16% for the AM samples. During the creep tests at 650 °C, the creep stress exponent was found in the range of 8–18, indicating that the deformation at the examined nano/micro scale is controlled by the dislocation climb mechanism.

In this study, as-cast and cold-rolled Zr63.78Cu14.72Ni10Al10Nb1.5 bulk metallic glass (BMG) samples were subjected to 20, 70, 120, and 170 cryogenic thermal cycles prior to fracture toughness testing. Thermal cycling raised the fracture toughness by promoting plastic deformation and stable crack growth, with the most significant increase occurring after the first 20 thermal cycles. Thermally cycled samples showed more tortuous crack paths and stable crack propagation left periodic blunting marks spaced at ∼57.5 μm on the fracture surface corresponding to each increment of crack advance. Microhardness mapping revealed a microstructure of hard and soft domains (∼63 μm × 105 μm), and thermal cycling heterogeneously softened the hard domains while the soft domains remained apparently unchanged. In addition to the observed softening, large increases in the relaxation enthalpy, and thus the average free volume, were found over the first ∼70 thermal cycles. While cold rolling the samples prior to the thermal cycling did not raise the mean fracture toughness values, the scatter was reduced compared to as-cast thermal cycled samples. This was attributed to the introduction of shear bands giving a more repeatable initial microstructure than casting.

Fatigue crack growth is analyzed for steady state and overload conditions. The model combines an elastic-plastic strain gradient hardening material and an irreversible cohesive zone model. Plastic strain gradients are found not to affect steady-state fatigue crack growth but play a key role in the overload response. Plastic strain gradient hardening lowers plastic strain magnitudes and alters the spatial distribution of plastic strain. This leads to reduced crack closure and higher crack growth rates during and after the overload. Using classical plasticity alone to describe fatigue crack growth following an overload is thus nonconservative.

Crack growth mechanisms for Alloy 617 at 800 °C were investigated in air with specific emphasis on the transition from cycle-dependent to time-dependent crack growth mechanisms in the creep-fatigue regime. Crack growth studies were conducted using compact tension samples, a load ratio of 0.5, and triangular 5 Hz, 0.33 Hz, and 0.05 Hz waveforms, a trapezoidal 0.05 Hz waveform with 17 s hold time, and sustained loading. Fatigue crack growth rates were relatively insensitive to changes in frequency and hold times in air up to ∆K ≈ 11.5 MPa√m for R = 0.5, i.e, Kmax = 23 MPa√m. Above this threshold, the onset of time dependent crack growth was observed via a creep void nucleation and coalescence mechanism for triangular and trapezoidal waveforms with a loading frequency of 0.05 Hz, and during sustained loading. An estimate of the threshold for stress assisted grain boundary oxidation (SAGBO) crack growth was calculated to be 23 MPa√m, and oxidized grain boundaries observed near the crack tip were mostly uncracked, suggesting the SAGBO threshold was not reached before the onset of the void nucleation mechanism. A comparison of results across all available studies suggests that a threshold-based transition from cycle- to time-dependent crack growth at 800 °C likely exists. However, the stress intensity factor does not maintain similitude to accurately define a threshold across studies. Thus, gaining an understanding of the crack tip stress states that define the various time dependent mechanisms should be considered in future work.

Dynamic cell‐culture materials that can change mechanical properties in response to extrinsic stimuli are emerging as promising tools for cell and tissue engineering research. However, most of these techniques involve a one‐way stiffening or softening through changes in the materials chemistry, which does not allow reversibility. Here, the incorporation of superparamagnetic iron‐oxide nanoparticles within poly(ethylene glycol) hydrogels as dynamic cell culture materials is demonstrated. Using simple permanent magnets and adipose‐derived stem cells, a near twofold increase in cell spread area and an accompanying 20% enrichment in cells expressing alpha‐smooth muscle actin is seen. This platform provides a means to study relationships between dynamic stiffening and cell behavior, using permanent magnets and clinically viable composite materials, with scope for use as a tool to enrich the myofibroblast population in stromal cells.

Journal of materials research 36(11), 2325 - 2336 (2021). doi:10.1557/s43578-021-00187-5, High strain rate micromechanical testing can assist researchers in elucidating complex deformation mechanisms in advanced material systems. In this work, the interactions of atomic-scale chemistry and strain rate in affecting the deformation response of a Zr-based metallic glass was studied by varying the concentration of oxygen dissolved into the local structure. Compression of micropillars over six decades of strain rate uncovered a remarkable reversal of the strain rate sensitivity from negative to positive above ~ 5 s$^{���1}$ due to a delocalisation of shear transformation events within the pre-yield linear regime for both samples, while a higher oxygen content was found to generally decrease the strain rate sensitivity effect. It was also identified that the shear band propagation speed increases with the actuation speed, leading to a transition in the deformation behaviour from serrated to apparent non-serrated plastic flow at ~ 5 s$^{���1}$., Published by Cambridge Univ. Press, Cambridge [u.a.]

Metallic glasses (MGs) with superior catalytic performance have recently been recognized as attractive candidates for wastewater treatment. However, further improving their performance will require knowledge of how to precisely regulate their electronic structures via compositional control. Here, two Fe-based MGs (Fe

Objectives Understand how discontinuous short glass fibers and braided long fibers can be effectively used to reinforce a resin modified glass ionomer cement (RMGIC) for carious lesion restorations. Methods Two control groups (powder/liquid kit and capsule) were prepared from a light cured RMGIC. Either discontinuous short glass fibers or braided polyethylene fiber ribbons were used as a reinforcement both with and without pre-impregnation with resin. For the former case, the matrix was the powder/liquid kit RMGIC, and for the latter case the matrix was the capsule form. Flexural strength was evaluated by three-point beam bending and fracture toughness was evaluated by the single-edge V-notch beam method. Compressive strength tests were performed on cylindrical samples. Results were compared by analysis of variances and Tukey’s post-hoc test. Flexural strength data were analyzed using Weibull statistical analysis. Results The short fiber reinforced RMGIC both with and without pre-impregnation showed a significant increase of ∼50% in the mean flexural strength and 160–220% higher fracture toughness compared with the powder/liquid RMGIC control. Reinforcement with continuous braided fibers gave more than a 150% increase in flexural strength, and pre-impregnation of the braided fibers with resin resulted in a significant flexural strength increase of more than 300% relative to the capsule control. However, for the short fiber reinforced RMGIC there was no significant benefit of resin pre-impregnation of the fibers. The Weibull modulus for the flexural strength approximately doubled for the fiber reinforced groups compared to the control groups. Finally, compressive strength was similar for all the groups tested. Significance By using a RMGIC as a matrix, higher flexural strength was achieved compared to reported values for short fiber reinforced GICs. Additionally, the short fibers provided effective toughening of the RMGIC matrix by a fiber bridging mechanism. Finally, continuous braided polyethylene fibers gave much higher flexural strength than discontinuous glass fibers, and their effectiveness was enhanced by pre-impregnation of the fibers with resin.

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 than for the weld metal, with the latter containing much finer, well-dispersed M6C carbides.

In this study, a machine-learning approach based on Gaussian process regression was developed to identify the optimized processing window for laser powder bed fusion (LPBF). Using this method, we found a new and much larger optimized LPBF processing window than was known before for manufacturing fully dense AlSi10Mg samples (i.e., relative density ≥ 99%). The newly determined optimized processing parameters (e.g., laser power and scan speed) made it possible to achieve previously unattainable combinations of high strength and ductility. The results showed that although the AlSi10Mg specimens exhibited similar Al-Si eutectic microstructures (e.g., cell structures in fine and coarse grains), they displayed large difference in their mechanical properties including hardness (118 - 137 HV 10), ultimate tensile strength (297 - 389 MPa), elongation to failure (6.3 - 10.3%), and fracture toughness (9.9 - 12.7 kJ/m2). The underlying reason was attributed to the subtle microstructural differences that were further revealed using two newly defined morphology indices (i.e., dimensional-scale index Id and shape index Is) based on several key microstructural features obtained from scanning electron microscopy images. It was found that in addition to grain structure, the sub-grain cell size and cell boundary morphology of the LPBF fabricated AlSi10Mg also strongly affected the mechanical properties of the material. The method established in this study can be readily applied to the LPBF process optimization and mechanical properties manipulation of other widely used metals and alloys or newly designed materials.

A Zr-based bulk metallic glass produced using selective laser melting (SLM) was compared to the same alloy fabricated using traditional suction-casting. Analysis of the fracture toughness through single edge notched beam bending experiments showed a significantly reduced damage tolerance for the laser-processed material (KQ ~ 138.0 ± 13.1 → 28.7 ± 3.7 MPa √m), even though X-ray diffraction and microhardness responses were identical. Using uniaxial quasistatic micro-pillar compression, it was found that as-cast samples more readily underwent shear transformations (evidenced through discrete load drops) below the nominal 0.2% yield stress, which was connected to the higher macroscopic toughness. Differential scanning calorimetry demonstrated that the increased barrier to shear transformation for the SLM material could not be explained by the relative relaxation states. Rather, it was attributed to the greater dissolved oxygen concentration in the laser-processed material, which is postulated to decrease atomic mobility in the structure and thereby increase the activation energy required to initiate shear transformations.

A Gaussian process regression-based machine learning approach was used to establish a processing window optimized for high density additive manufacturing of a 2 vol% TiCN reinforced AlSi10Mg composite by laser powder bed fusion. The optimized window for TiCN reinforced AlSi10Mg was found to be smaller than for AlSi10Mg. Within the optimized window, it was found that the Si eutectic cell size can be increased by raising the laser power/scanning speed at the constant energy density of 50 J/mm3 to control the tensile properties of the fabricated composites.

Objective: To compare the tolerability and mechanical tensile strength of acute skin wounds closed with nylon suture plus a novel suture bridge device (SBD) with acute skin wounds closed with nylon suture in a porcine model. Approach: Four Yucatan pigs each received 12 4.5 cm full-thickness incisions that were closed with 1 of 4 options: Suture bridge with nylon, suture bridge with nylon and subdermal polyglactin, nylon simple interrupted, and nylon simple interrupted with subdermal polyglactin. Epithelial reaction, inflammation, and scarring were examined histologically at days 10 and 42. Wound strength was examined mechanically at days 10 and 42 on ex vivo wounds from euthanized pigs. Results: Histopathology in the suture entry/exit planes showed greater dermal inflammation with a simple interrupted nylon suture retained for 42 days compared with the SBD retained for 42 days (p

Novel Zr63.78Cu14.72Ni10-xCoxAl10Nb1.5 bulk metallic glasses (BMGs) were prepared with progressively increasing amounts of Co substituted for Ni. Critical casting thicknesses were in the range of 4–5 mm, indicating a good glass forming ability. Transmission electron microscopy (TEM) of the as-cast amorphous structure revealed primary glassy phase separated regions a few dozens of nanometers in diameter. High yield strength (∼1495 MPa), fracture toughness (∼55 MPa√m), and strong strain hardening behavior were observed. Deformation induced secondary phase separation (