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Compact microchannel heat exchanger designs for supercritical CO2 power cycles are valued for equipment size reduction and increased heat transfer. They can be fabricated via transient-liquid phase...

This work evaluated the technical basis of using laser direct energy deposition (DED) additive manufacturing (AM) as a rapid alloy screening method to study the phase transformation of second phase particles and recrystallization behavior of Al-Mn alloy AA3104 throughout the steps of thermomechanical processing. The study focused on assessing the differences between DED and DC-cast AA3104 alloy after homogenization and hot rolling. The fast cooling and repeated in situ thermal cycles during DED AM resulted in different phase transformation behavior compared to conventional DC-cast alloys. DED alloys exhibited a higher fraction of α-Al (Fe,Mn)-Si particles, more uniform particle distribution, and stronger cube texture in the as-fabricated condition. Homogenization promoted Al6(Fe,Mn) to α-Al (Fe,Mn)-Si phase transformation in both DED and DC-cast alloys. After homogenization, DED alloys exhibited two times as many coarse α particles in area fraction as DC-cast alloys but fewer nanoscale dispersoids. These unique material characteristics in DED alloys were responsible for easier recrystallization after hot rolling and annealing. While the differences existed, DED and DC-cast AA3104 alloys demonstrated a similar trend in phase transformation and recrystallization, strongly reinforcing that DED AM can support high-throughput Al alloy development.

The feasibility of using laser direct energy deposition (DED) additive manufacturing (AM) to synthesize a commercial, aluminum-manganese alloy of the 3000 series was evaluated by comparing the microstructures of AM and direct-chill (DC) cast alloys. The purpose of this work was to establish a baseline for accelerating Al alloy discovery using combinatorial materials synthesis. Feedstock alloy powder was prepared by mixing pure metal element or binary alloy powders via ball-milling and fabricating bulk samples using laser DED AM. Compositional accuracy of both powder feedstock and laser DED AM samples was controlled within 10% of the target. The effect of homogenization on the evolution of second-phase particles as a function of temperature and time was found to be similar in both laser DED AM and DC-cast materials.

Introduction In the emergency department, the diagnosis of an Achilles tendon rupture (ATR) is reportedly missed in greater than 20% of cases. A limited number of studies evaluate the use of cadaver models as a potential ultrasound teaching and training modality. We hypothesize that emergency medicine residents can effectively utilize point-of-care ultrasound (POCUS) on cadaver models and a focused teaching intervention to assess their ability to detect ATRs. Methods A prospective study of 23 EM residents was performed. All participants in the study were divided into two learner groups: (a) independent and (b) hands-on. The independent learner group received a 30-minute online didactic lecture demonstrating how to diagnose ATRs. The hands-on learner group received direct instruction on cadaver lower leg models with a ruptured and normal Achilles tendon (AT). Both groups then participated in identifying either normal or ruptured ATs on six cadaver lower leg models. Results The sensitivity and specificity were 89% and 82% in the independent learner group 96% and 100% in the hands-on learner group, respectively. The overall sensitivity and specificity were 91% and 88%, respectively. There was a trend toward successful identification with increased years of residency training. Conclusions In this study, lower leg and ankle cadaver models were found to be as effective as an independent learner model for potential POCUS teaching and training modality in both novice and more advanced trainees.

Objectives In 2015, the American Academy of Pediatrics (AAP) released a policy statement regarding point-of-care ultrasonography (POCUS) by pediatric emergency physicians, which included recommendations on education and training. In the 3 years since the AAP policy statement and its accompanying technical report were published, it is unclear which aspects of the recommendations set forth by this policy have been instituted by POCUS programs throughout the country. The objective of this study was to conduct a survey of pediatric emergency medicine (PEM) fellowship directors throughout the United States regarding the current state of education and training of POCUS in their department. Methods We conducted an online survey of all PEM fellowship program directors in the United States between April 1, 2018, and July 31, 2018. Results Of the 78 PEM fellowship program directors contacted, 62 (79.5%) responded. The majority reported having an ultrasound curriculum in place to educate their fellows (77%). Fellows are being taught using a variety of educational strategies. The most commonly reported barriers were lack of qualified faculty available for training (62.9%), lack of confidence or comfort in using the existing ultrasound machine(s) in their department (54.8%), and physician resistance to using new technology (50%). The majority of programs reported having processes in place for credentialing (56%) and quality assurance (72.6%). Whereas 77.4% have a system for archiving POCUS studies after they are performed, only half of the programs report utilization of middleware for their archival system. Compliance with documentation varied significantly between programs. Conclusions Our survey results demonstrate that, although there is still room for improvement, POCUS programs have succeeded in many of the goals set forth by the 2015 AAP policy statement, such as establishing and growing an ultrasound curriculum and using various strategies to educate PEM fellows.

An improved understanding of high-temperature alloy oxidation is key to the design of structural materials for next-generation energy conversion technologies. An often overlooked, yet fundamental aspect of this oxidation process concerns the fate of the metal vacancies created when metal atoms are ionized and enter the growing oxide layer. In this work, we provide direct experimental evidence showing that these metal vacancies can be inseparably linked to the oxidation process beginning at the very early stages. The coalescence of metal vacancies at the oxide/alloy interface results initially in the formation of low-density metal and eventually in nm-sized voids. The simultaneous and subsequent oxidation of these regions fills the vacated space and promotes adhesion between the growing oxide and the alloy substrate. These structural transformations represent an important deviation from conventional metal oxidation theory, and this improved understanding will aid in the development of new structural alloys with enhanced oxidation resistance. Instead of annihilating, vacancies created early during high-temperature oxidation of a nickel superalloy coalesce into low-density regions. A team led by Richard Oleksak from the National Energy Technology Laboratory in Oregon, USA, used scanning transmission electron microscopy and atom probe tomography to characterize the surface of a nickel superalloy early in the oxidation process. Under the oxide layer, the metal substrate had many voids, and was rich in aluminum oxide. Contrary to conventional metal oxidation theory, vacancies coalesced to form clusters and nanovoids near the oxide/alloy interface while aluminum was selectively oxidized, creating a region of low-density metal rich in aluminum oxide under the surface, which was then incorporated into the growing surface oxide. Research into early and long-term oxidation mechanisms will help better design stable alloys.

Transient-liquid-phase bonding using Ni-P as an interlayer has been developed for H230 Ni-Cr-W solid-solution-strengthened Ni-based alloy. Two process parameters—composition of the interlayer and bonding time—have been varied to optimize the mechanical properties. H230 has been bonded into two sets of stacks (set I and II) for 8 and 4 hours using Ni-12P and Ni-6P interlayer, respectively, (wt pct) at 1423 K (1150 °C) and 12.7 MPa. The microstructure of both the stacks has three distinct regions—the joint centerline which showed the presence of pores, an isothermally solidified zone (ISZ) which did not have any carbide precipitates and base H230. Transmission electron microscopy and atom probe tomography showed a uniform microstructure, and an absence of any deleterious phases at the joint and in ISZ. Set I and set II had a yield strength of 76 and 86 pct of that of the H230 sheet, tested at 1023 K (750 °C). The measured elongation at fracture was negligible, but the fracture surfaces revealed a ductile cup-and-cone-type fracture occurring through the ISZ/joint region. Examination of broken tensile samples revealed that the plastic strain was constrained to within one joint region through which fracture occurred.

The relationship between precipitate evolution, martensitic transformation temperatures, hardness, and functional load-bias behavior has been analyzed for a Ni50.8Ti34.2Zr15 (at.%) alloy. In the solutionized condition, the alloy was fully austenitic and no transformation (at least to −90 °C) was observed. Upon aging at 550 °C, the onset of a martensitic transformation (Ms), as determined by differential scanning calorimetry, was observed at approximately −10 °C and 75 °C after 24 and 300 h, respectively. Electron diffraction identified the precipitation of the orthorhombic H-phase within the B2 matrix. When the inter-precipitate spacing was ~12 nm, a greater undercooling was necessary to initiate the martensitic transformation due to overlapping strain fields of the precipitates. As the precipitates coarsened with aging time, a corresponding increase in the inter-precipitate spacing occurred and the chemical partitioning effects between the matrix and precipitate, as determined by atom probe tomography, began to dominate the transformation behavior resulting in an increase in transformation temperatures. For selected aging conditions, the load-biased shape memory behavior was determined under compressive and tensile loading using uniaxial constant-force thermal cycling experiments. A tension-compression asymmetry was noted with larger transformation strains in tension than compression at constant stresses up to 400 MPa. A recoverable transformation strain of 3% was observed in the sample aged for 4 h at 550 °C under a tensile stress of 400 MPa, which is the largest recoverable strain currently reported for a precipitation-strengthened NiTiZr alloy.

Composition analysis of carbide and carbo-nitride precipitates was performed for two Nb-Ti microalloyed steels with yield strengths of 750 and 580 MPa using an atom probe study. In the high-Ti 750 MPa steel, Ti-rich (Ti,Nb)(C,N) and Ti-rich (Ti,Nb)(C) precipitates were observed. In the high-Nb 580 MPa steel, a Ti-rich (Ti,Nb)(C,N) precipitate and (Ti,Nb)(C) clusters were noted. These (Ti,Nb)(C) clusters in the high-Nb 580 MPa steel were smaller than the (Ti,Nb)(C) precipitates in high-Ti 750 MPa steel. In general, a larger number of precipitates were found in the high-Ti 750 MPa steel. This difference in the number density of the precipitates between the two steels is attributed to the difference in Ti content. Combining the atom probe tomography results and thermodynamic calculations, the precipitation sequence in these alloys was inferred to be the following: as the temperature decreases, TiN precipitates out of the solution with successive (Ti,Nb)(C,N) layers of varying composition forming on these Ti-rich precipitates. Once N is depleted from the solution, a second set of (Ti,Nb)(C) precipitates in a similar manner in the matrix and also onto the carbo-nitride phase. This observation is consistent with previous observations in high-strength low-alloy steels containing comparable amounts of only Nb. It was noted that the amount of Nb, Nb/(Nb + Ti), in the precipitates decreased from 0.20 to 0.04 with the size of the precipitate. We believe that this is due to the Nb supersaturation in the matrix when these precipitates nucleate.

Two experimental bcc -Cu- and B2–NiAl-precipitation-strengthened ferritic steels with 6.3 at. % and 12.4 at. % Cu + Mn + Ni + Al, 950 MPa and 1600 MPa yield strength respectively, were studied. Atom probe tomography showed that the volume fraction and number density of NiAl-type precipitates in the heavier alloyed steel (designated as CF-9 ) is ∼60–70 times greater than those in the lighter alloyed steel (designated as CF -2). This is attributed to the smaller lattice misfit between these NiAl-type precipitates and the ferritic matrix in CF- 9 due to more incorporation of Mn atoms on the Al sub-lattice in the B2 NiAl unit cell. Loading rate sensitivity of hardness was measured for CF -2, CF -9 and SAE -1090, which does not have bcc -Cu precipitates. Results show that even though CF -2 and CF -9 have double and triple the strength of SAE -1090 respectively, their hardness shows weaker dependence on loading rate. This is attributed to the presence of bcc -Cu precipitates in CF -2 and CF -9 providing athermal activation of nearby screw dislocation motion. Auger electron spectroscopy studies of CF -9 samples reveal Cu segregation on grain boundaries. The observed Cu segregation is believed to be partly responsible for the lower elongation-to-failure of CF -9 compared with CF -2.

The precipitation of the P-phase in Ni–Ti–Pd and Ni–Ti–Pt shape memory alloys has been shown to dramatically increase the martensitic transformation temperature and strength in Ni-rich ternary alloys, yet little is known about the phase's compositional stability. Therefore, the compositional limits of the P-phase have been systematically studied by varying the Pd and Ni content while maintaining the general P-phase Ti 11 (Ni + Pd) 13 stoichiometry. Each alloy was solutionized at 1050 °C followed by water quenching, and aging at 400 °C for 100 h. Four distinct phases were identified by electron and x-ray diffraction: Ti 2 Pd 3 , B2 NiTi, P- and P1-phases. The latter precipitate phases became more stable with increasing Ni at the expense of the Pd content. Atom probe tomography revealed the P-phase composition to be 45.8Ti–29.2Ni–25Pd (at.%) or Ti 11 (Ni 7 Pd 6 ) as compared to the P1-phase 44.7Ti– 45.8Ni–9.4Pd (at.%) or Ti 5 Ni 5 Pd.

A series of bulk nanostructured Fe–Ni–Zr oxide-dispersion-strengthened (ODS) alloys were synthesized using high energy mechanical alloying and consolidated using high temperature equal channel angular extrusion. The resultant microstructures are composed of nano/ultrafine or micrometer-sized grains with larger intermetallic precipitates and small Zr oxide clusters (

Creep performance of a potential heat exchanger alloy, Haynes 230 was investigated. To simulate mechanical performance of a heat exchanger, sheet material of Haynes 230 transient liquid phase (TLP) bonded together. Sheets were plated on both sides with a Ni–P compound, subsequently stacked and TLP bonded together. Duplicate creep tests show low scatter in creep results, meaning a good repeatable joint was formed by TLP bonding. Overall creep performance showed less ductility and shorter times to failure than specimens originating from plate material. Evolution of a phosphorous compound at the bond line was observed and thought to potentially reduce ductility of the TLP bonded alloy.

The effect of Hf (0–1 at.%) additions in a Ni-Ti-Pd alloy on P-phase precipitation and martensitic transformations was studied. The addition of hafnium resulted in the refinement of precipitates with an increase in number density. The overlapping strain fields created due to the decrease in inter-precipitate spacing are suspected to reduce the matrix volume to be less than the critical free volume size needed for the martensitic transformation over the temperature range studied (183–573 K). Hafnium was also found to delay the aging time to achieve peak hardness, suggesting a reduction in growth and coarsening kinetics.

As the length scale of materials decreases to the nanometer regime, grain boundaries occupy a relatively larger volume fraction. Consequently, they play an important role in stabilizing nanocrystalline systems. This review looks at the role of solute segregation to grain boundaries in stabilizing such systems. In recent years, grain size stabilization from solute segregation has led to new types of thermodynamic stability maps as a materials design tool. We propose to extend and adapt these concepts of grain boundary solute segregation as a stabilizing effect to thin film stress states. A recent study on Fe–Pt alloy films, where one species enriched the boundaries, was shown to manipulate the stress from tensile-to-compressive as a function of composition. This suggests that intrinsic segregation can be used as a tunable variable to manipulate stress states, analogous to changing film processing parameters, such as deposition rate and pressure. The application of such solute segregation is at the precipice of new opportunities in materials design of thin films.

Background: Volume overload in patients on hemodialysis (HD) is an independent risk factor for cardiovascular mortality. B-lines detected on lung ultrasound (BLUS) assess extravascular lung water. This raises interest in its utility for assessing volume status and cardiovascular outcomes. Methods: End-stage renal disease patients on HD at the Island Rehab Center being older than 18 years were screened. Patients achieving their dry weight (DW) had a lung ultrasound in a supine position. Scores were classified as mild (0-14), moderate (15-30), and severe (>30) for pulmonary congestion. Patients with more than 60 were further classified as very severe. Patients were followed for cardiac events and death. Results: 81 patients were recruited. 58 were males, with a mean age of 59.7 years. 44 had New York Heart Association (NYHA) class 1, 24 had class 2, and 13 had class 3. In univariate analysis, NYHA class was associated with B-line classes (p = 0.0049). Multivariate Cox regression analysis showed the independent predictive value of BLUS class for mortality and cardiac events with a heart rate of 2.98 and 7.98 in severe and very severe classes, respectively, compared to patients in the mild class (p = 0.025 and 0.013). Conclusion: At DW, BLUS is an independent risk factor for death and cardiovascular events in patients on HD.

A free-floating right heart thrombus is often a harbinger of a massive pulmonary embolism and must be diagnosed and treated rapidly in order to avoid significant adverse sequelae. We present the case of an 84-year-old female who presented with two days of dyspnea and was hypotensive on arrival. Bedside ultrasound was performed by the emergency physician and showed a large, mobile right heart thrombus leading to immediate administration of a thrombolytic. In this case, bedside ultrasound was utilized to help further delineate clinical care in a progressively worsening patient, leading to a potentially lifesaving treatment. [West J Emerg Med. 2015;16(1):178–180.]

Commercially pure nickel (Ni) was thermomechanically processed to promote an increase in Σ3 special grain boundaries. Engineering the character and chemistry of Σ3 grain boundaries in polycrystalline materials can help in improving physical, chemical, and mechanical properties leading to improved performance. Type-specific grain boundaries (special and random) were characterized using electron backscatter diffraction and the segregation behavior of elements such as Si, Al, C, O, P, Cr, Mg, Mn, B, and Fe, at the atomic level, was studied as a function of grain boundary character using atom probe tomography. These results showed that the random grain boundaries were enriched with impurities to include metal oxides, while Σ3 special grain boundaries showed little to no impurities at the grain boundaries. In addition, the influence of annealing time on the concentration of segregants on random grain boundaries was analyzed and showed clear evidence of increased concentration of segregants as annealing time was increased.

Only few cases of Eptopic cilia have been reported in literature. Anterior ectopic cilia cause no apparent ocular symptoms and can be surgically excised for cosmetic improvement. We report a case of a 28-year-old male with anterior ectopic cilia in association with hypermetropic anisometropic amblyopia. Only 15 cases of anterior ectopic cilia have been reported in literature. Few of them were associated with some conditions such as choristoma, aberrant lacrimal glands, atopic eczema, nail–patella syndrome, and hypochromic nevus. To the best of our knowledge, this is the first reported case of anterior ectopic cilia associated with hypermetropic anisometropic amblyopia. No underlying common causative disorder became evident. The observed association was considered as coincidental.