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At least 235 records · Page 13

Non-Equilibrium Superconductivity and Magnetic Pair Breaking in Perovskite Half-Metallic Ferromagnet-Insulator-Superconductor (F-I-S) Heterostructures

The effect of spin-polarized quasiparticle currents on the critical current density (J-c) of cuprate superconductors is studied in perovskite F-I-S heterostructures as a function of insulator thickness and of underlying magnetic materials. A pulsed current technique is employed to minimize extraneous Joule heating on the superconductor. At temperatures near T-c, F-I-S samples with insulator thicknesses\1e2nm show precipitous decrease in J_c as current injection (I_m) is increased. In contrast, J_c in a controlled sample with a substituted non-magnetic material (N-I-S) exhibit no dependence on I_m. Similarly, a F-I-S sample with a 10 mn insulating barrier also show little J_c effect versus I_m. At low temperatures with I_m = 0, significant suppression of J-c is observed only in the thin barrier F-I-S samples, although T_c and the normal-state resistivity of all samples are comparable. These phenomena can be attributed to the Cooper pair breaking induced by externally-injected and internally-reflected spin-polarized quasiparticle currents. We estimate an order of magnitude range for the spin diffusion length of 100 nm to 100\ mum.

Fu, C.-C.↗

Surface characterization of selected LDEF tray clamps

The surface characterization of chromic acid anodized 6061-T6 aluminum alloy tray clamps has shown differences in surface chemistry depending upon the position on the Long Duration Exposure Facility (LDEF). Water contact angle results showed no changes in wettability of the tray clamps. The overall surface topography of the control, trailing edge(E3) and leading edge(D9) samples was similar. The thickness of the aluminum oxide layer for all samples determined by Auger depth profiling was less than one micron. X-ray photoelectron spectroscopy (XPS) analysis of the tray clamps showed significant differences in the surface composition. Carbon and silicon containing compounds were the primary contaminants detected.

Cromer, T. F.↗

Growth of Native Oxides of Niobium Thin Films for Superconducting Qubits with Etching Chemistry

Niobium thin films have been broadly applied in building superconducting qubits for quantum computing hardware. While improvements have been made by device engineering efforts, scaling the energy-sensitive quantum system requires materials study for further improvements. In this study, we performed XPS and ToF-SIMS analysis for Nb thin films across samples with different manufacturing techniques. By varying the air exposure time of the samples, this research comparatively investigates the chemical and depth profile of native oxides before and after the etching process. We observe a rapid logarithmic growth of oxide thickness across all samples and the dominant presence and growth of Niobium pentoxide in atomic percentage concentration on the surface. This comparative study provides insight into oxides mitigation strategies and correlation with qubits performance.

Lei, Zhicheng↗

Effects on LDEF exposed copper film and bulk

Two forms of copper were exposed to the Long Duration Exposure Facility (LDEF) Mission 1 environment: a copper film initially 74.2 plus or minus 1.1 nm thick sputter coated on a fused silical flat and a bulk piece of oxygen free, high conductivity (OFHC) copper. The optical density of the copper film changed from 1.33 to 0.70 where exposed and the film thickness increased to 106.7 plus or minus 0.5 nm where exposed. The exposed area appears purple by reflection and green by transmission for the thin film and maroon color for the bulk copper piece. The exposed areas increased in thickness, but only increase in the thickness of thin film samples could be readily measured. The increase in film thickness is consistent with the density changes occurring during conversion of copper to an oxide. However, we have not been able to confirm appreciable conversion to an oxide by x ray diffraction studies. We have not yet subjected the sample to e-beams or more abusive conditions out of concern that the film might be modified.

Peters, Palmer N.↗

LDEF SP-HVDE (Space Plasma-High Voltage Drainage Experiment) post-flight results: Leakage current and discharge

TRW designed and fabricated two identical SP-HVDE trays which were flown in the NASA LDEF (Long Duration Exposure Facility) for 5.75 years in the LEO (low earth orbit) environment. One tray was placed near the leading edge and one near the trailing edge, and investigations were performed to compare the environmental interactions on the dielectric samples of the two trays. Each tray consisted of six assemblies with Kapton dielectric samples of varying thicknesses (i.e., 2 mils, 3 mil, and 5 mils) biased under +/- 300 V, +/- 500 V, and +/- 1000 V. The original objective was successfully achieved by measuring the first in-flight average leakage current through the samples. Less than 5 percent of the post-flight coulometers behaved anomalously. The data should be valuable to the design and evaluation of spacecraft with high voltage systems. M/D (micrometeoroid and debris) impacts over the dielectric samples were examined using a SEM (Scanning Electron Microscope) and an EDS (Energy Dispersive x-ray Spectrometer). These impact sites were sprayed by silver which were most likely caused either by the impact or a 'local ESD' (electrostatic discharge).

Yaung, J. Y.↗

Effect of processing parameters and strut dimensions on the microstructures and hardness of stainless steel 316L lattice-emulating structures made by powder bed fusion

In this study, we present the effects of input processing parameters and strut thickness (in square struts) on microstructure and properties in laser powder bed fusion additively manufactured stainless steel 316L lattice-emulating structures. Lattice-emulating X-structures with square cross-sections of 1.5, 1.0, and 0.5 mm were fabricated using three different parameter sets with varying power, speed, and therefore, linear energy density. Grain size and morphology were shown to be dictated by epitaxial growth, which was dependent on weld pool morphology. Additionally, grain size and morphology were shown to change across the thickness direction of the struts (from the bottom inclined surface to the top inclined surface). The spatial variation in grain size was reflected by changes in hardness through the thickness of each strut. The 0.5 mm struts exhibited more significant grain elongation in the strut direction and larger sub-grain solidification cell diameters than their thicker counterparts. The larger sub-grain solidification cell diameters in the 0.5 mm samples resulted in correspondingly lower hardness values when compared to samples of higher thicknesses.

36 MATERIALS SCIENCE↗

Preliminary Results of the Third Test Series of Nonmetal Material Flammability Evaluation In SKOROST Apparatus on the Space Station Mir

The work has been done according to the US/Russian Joint Project "Experimental Evaluation of the Material Flammability in Microgravity" a continued combustion study in the SKOROST test apparatus on the OS Mir. The objective of the project was to evaluate the flammability and flame-spread rate for the selected polymer materials in low velocity flow in microgravity. Lately, the issue of nonmetal material combustion in microgravity has become of great importance, based on the necessity to develop the fire safety system for the new International Space Station (ISS). Lack of buoyant flow in microgravity reduces oxygen transfer into the combustion zone, which leads to flame extinction when the flow velocity is less than the limiting flow velocity V(sub lim) for the material. The ISS FGB fire-safety system was developed based on this phenomenon. The existence of minimum flow velocity V(sub lim) to sustain fire for the selected materials was determined both theoretically and experimentally. In the latter, it is shown that, even for thermally thin nonmetal materials with a very low oxygen index C(sub lim) of 12.5% (paper sheets with the thickness of 0.1 mm), a limiting flow velocity V(sub lim) exists at oxygen concentration Co(sub OX) = 17-21%, and is about 1.0 - 0.1 cm/sec. This might be explained by the relative increase in thermal losses due to radiation from the surface and from the gaseous phase. In the second series of experiments in Skorost apparatus on Orbital Station Mir the existence of the limiting flow velocity V(sub lim) for combustion was confirmed for PMMA and glass-epoxy composite strip samples 2 mm thick at oxygen concentration C(sub OX) = 21.5%. It was concluded that V(sub lim) depends on C(sub OX) for the PMMA sample with a low oxygen index of 15.5%, the limiting flow velocity V(sub lim) was less than 0.5 cm/sec, and for the glass-epoxy composite sample with a high oxygen index of 19%, the limiting flow velocity V(sub lim) was higher than 15 cm/sec. As of now only those materials that maintain their integrity during combustion were investigated. The materials that disintegrate when burning present more danger for fire safety because the flame can spread farther with the parts of the structure, ejected melt drops, et cetera. Materials such as polyethylene are of great interest since they form a lengthy melt zone during the combustion in normal gravity. This melt zone generates drops of liquids that promote faster flame spread compared to usual combustion. The preliminary results of polyethylene insulation flammability evaluation in microgravity are shown in the NASA Wire Insulation Flammability (WIF) experiment during Space Shuttle flight STS-50. A lot of interesting data was collected during the WIF test program. However, one of the most important results was that, in microgravity, the extinction of the polyethylene occurred almost immediately when the flow of relatively low oxygen concentration (C(sub OX)=21%) was stopped. The purpose of the work reported here is to expand the existing data base on material flammability in microgravity and to conduct the third series of the space experiment using Skorost apparatus on Orbiatl Station Mir with melting polymers, which might increase the probability of fire and its propagation in ventilated microgravity environment of orbiting spacecraft.

Ivanov, A. V.↗

Superconductivity devices: Commercial use of space

A YBCO thick film containing 20 percent Ag2O with a T(sub c) of 86.8 K and J(sub c) of 108 A/sq cm was obtained. The film was fabricated by a two-step firing process, i.e., firing the film at 1000 C for 10 minutes and annealing at 970 C for 30 minutes. The two-step firing process, however, was not suitable for the multiple-lead YBCO sample due to the formation of the 211 green phase at 1000 C in the multiple-lead YBCO sample. A BSCCO thick film printed on a MgO coated MSZ substrate and fired at 845 C for 2 hours exhibited a superconducting behavior at 89 K. Because of its porous microstructure, the critical current density of the BSCCO thick film was limited. This report also includes the results of the YBCO and BSCCO materials used as oxide electrodes for ferroelectric materials. The YBCO electroded PLZT showed higher remanent polarization and coercive field than the sample electroded with silver paste. A higher Curie temperature for the PLZT was obtained from the YBCO electroded sample. The BSCCO electroded sample, however, exhibited the same Curie temperature as that of a silver electroded sample. Dissipation factors of the ferroelectric samples increased when the oxide electrode was applied.

Haertling, Gene↗

Flamelet Formation In Hele-Shaw Flow

A Hele-Shaw flow apparatus constructed at Michigan State University (MSU) produces conditions that reduce influences of buoyancy-driven flows. In addition, in the MSU Hele-Shaw apparatus it is possible to adjust the heat losses from the fuel sample (0.001 in. thick cellulose) and the flow speed of the approaching oxidizer flow (air) so that the "flamelet regime of flame spread" is entered. In this regime various features of the flame-to-smolder (and vice versa) transition can be studied. For the relatively wide (approx. 17.5 cm) and long (approx. 20 cm) samples used, approximately ten flamelets existed at all times. The flamelet behavior was studied mechanistically and statistically. A heat transfer analysis of the dominant heat transfer mechanisms was conducted. Results indicate that radiation and conduction processes are important, and that a simple 1-D model using the Broido-Shafizadeh model for cellulose decomposition chemistry can describe aspects of the flamelet spread process. Introduction

Wichman, I. S.↗

Characterizing The Mechanical Properties of Polyurethane Foams

The Department of Energy has many radioactive facilities that are on the path of deactivation and decommissioning (D and D). These facilities can sit cold and dark for many years before final disposition, and must be maintained to ensure no radiological release occurs in the interim. Improvements and additions to D and D tool sets can greatly: Save time and money, Reduce worker risk. Conventional fixatives widely used often take the form of paints or films that are not readily applicable to 3-dimensional void spaces. Foams are one promising platform that may offer solutions to a number of contaminated problem sets such as: Gloveboxes, Pipes, Tanks. SRNL is working to characterize various commercial foams that would encapsulate the interior volume of a given space and are capable of immobilizing any remaining contamination. One key performance metric of these foams is how well they will perform in an accident scenario. To this end, SRNL is researching the mechanical properties of these foams to ensure that the material can withstand the environment of application while maintaining structural integrity. ASTM standard E3191-18 served as a guiding document for this project, outlining the requirements that foaming fixatives used for the mitigation of radioactive contamination need to meet before being implemented. Objective: Quantification of the mechanical properties of 6 commercial polyurethane foams was performed using multiple ASTM standards to record measurements for: Compression testing: Flexible Foams, Force required to produce 50% compression, Rigid Foams, Compressive and apparent modulus, Point of 10% core deformation, The 'Zero Deformation' point, Compressive strength, Yield point. Tensile testing: Tensile strength, Tensile stress, Percent elongation. Experiment 1: An electromechanical compressive tester (MTS Criterion Series 43) was used to evaluate 6 foams (4 flexible, 2 rigid). Per ASTM D1621, each rigid foam was compressed at 10% of the measured thickness per minute until the sample was 13% of it's original thickness. Per ASTM D35/4, each flexible foam was pre-flexed twice to 80% original thickness at a rate of 250 mm/min, then compressed to 80% original thickness at a rate of 50 mm/min. Experiment 2: An electromechanical tensile tester (MTS Criterion Series 43) was used to evaluate 6 foams (4 flexible, 2 rigid). Per ASTM D1623, rigid foams were pulled apart at a rate of 1.27 mm/min until the sample broke. Per ASTM D35/4, flexible foams were pulled apart at a rate of 500 mm/min until the sample broke. The strongest material in both compression and tensile testing scenarios was found to be the rigid intumescent polyurethane Hilti foam. The experiments revealed that the Hilti foam in a tensile scenario had a peak stress value that was larger than the closest competitor by a factor of 2.3 and a compressive yield point that was larger than the closest competitor by a factor of 1.4, indicating that the Hilti foam is the best choice for implementation in mechanically harsh environments. The performance metrics measured can serve as a basis for future mechanical tests that would help set relevant ASTM standards (E3191) for intumescent polyurethane foams in fixating applications. Tests like surface adhesion, impact, and flame tests would serve as a better indicator as to how this material would perform in environmentally harsh scenarios often found in decommissioned nuclear facilities. Further tests of the foams' intumescent properties would also be important should these foams be implemented in environmentally harsh scenarios.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

Cooling Rate Study of Nickel-Rich Material During Thermal Treatment and Quench

To investigate quench cracking that results from water quenching after heat treatment of binary and Ni-rich material, cooling rates of specimens were measured during quenching and hardness post-thermal treatment. For specific applications binary Ni-Ti is customarily thermally treated and quenched to attain desired mechanical properties and hardness. However, one problem emerging from this method is thermal cracking, either during the heat treatment process or during the specimen's application. This can result in material and equipment failure as well as financial losses. The objective of the study is to investigate the internal cooling rate of 60-NiTi during quenching and determine possible factors causing thermal cracking. Cubic (1 in.3) samples of both material were heat treated in air at 1000 deg C for 2 hrs and quenched in room temperature water using two methods: (1) dropped in the water and (2) agitated in the water. Hardness of the two fore-mentioned methods was measured post heat treatment. Results indicate that the quenching method had an effect on cooling rate during quenching but hardness was observed to be essentially the same through the thickness of the samples.

Thermal Crack↗

Empirical Characterization and Modeling of Cohesive – to – Adhesive Shear Fracture Mode Transition due to Increased Adhesive Layer Thicknesses of Fiber Reinforced Composite Single – Lap Joints

Here, to ensure a strong adhesive bond, most standards and adhesive manufacturers specify a maximum adhesive gap of 1 mm when bonding fiber reinforced composite structures. In manufacturing large components, such as joining two halves of wind turbine blades, meeting this gap tolerance specification is impractical; gaps larger than 10 mm are common in large adhesively bonded composite structures using state-of-the-art manufacturing techniques. Currently, there is a lack of fundamental understanding of the failure mechanics of adhesive gaps larger than 3 mm. To create such understanding, glass fiber - acrylic thermoplastic composite panels bonded using different epoxy adhesives within single-lap joint samples with adhesive thicknesses of 0.1 mm, 0.3 mm, 1 mm, 3 mm, 5 mm, and 10 mm were sheared to failure. A transition from cohesive to adhesive failure was observed to occur about 1 mm to 3 mm joint thicknesses. Plotting the shear stress normalized by the ratio of the joint width to thickness as a function of the joint thickness normalized by the joint length is shown to result in the ability to fit simple empirically derived models of the cohesive-to-adhesive failure transition, regardless of the adhesive. Furthermore, using these normalized variables, all the observed cohesively failed specimens collapse to a single master curve, as do the adhesively failed specimens.

36 MATERIALS SCIENCE↗

Development of a Composite Material Aerodynamic Demise Model for the Object Reentry Survival Analysis Tool (ORSAT)

The reentry demise of fiber-reinforced polymer (FRP) composites is an increasing concern for modern spacecraft at end of life. Unlike traditional materials such as metals, shredding of the material by aerodynamic forces appears to be a major component of the reentry demise mechanism. This paper will describe a new mechanical, strength-based, material demise model for the Object Reentry Survival Analysis Tool (ORSAT) Version 7.1. The model is based on laboratory in-situ and residual strength tests of several FRP materials performed during the NASA Orbital Debris Program Office’s Phase II Composite Material Demise test campaign. To test the residual strength of partially charred FRP materials, the authors tested 107 rectangular shaped samples of different thicknesses that were previously exposed to high-enthalpy flow at the University of Texas at Austin’s Inductively Coupled Plasma Torch facility. Tests were performed under normal atmospheric conditions at NASA Johnson Space Center’s Experimental Impact Laboratory using a Chatillon TCD1000 tensile test machine configured with a three-point bending jig. Mean fracture load, residual strength, delamination, and flexural modulus were measured for each test. An engineering model of aeromechanical demise for each material was developed by correlating the measured residual strength of the samples with the duration and magnitude of the applied heat flux and the mass loss and char progression. This model has been implemented in ORSAT 7.1 for the built-in, charring carbon fiber/epoxy and charring glass fiber/epoxy material models. The new model was verified by calculating the demise of hundreds of FRP composite fragments of various shapes and sizes and checking the calculations for consistency, with specific focus on material characterization in one-dimension. Further tests are planned in hypersonic flow facilities to validate the assumptions used in the model.

Priscilla A. Mendoza↗

Development of a Composite Material Aerodynamic Demise Model for the Object Reentry Survival Analysis Tool (ORSAT)

The reentry demise of fiber-reinforced polymer (FRP) composites is an increasing concern for modern spacecraft at end of life. Unlike traditional materials such as metals, shredding of the material by aerodynamic forces appears to be a major component of the reentry demise mechanism. This paper will describe a new mechanical, strength-based, material demise model for the Object Reentry Survival Analysis Tool (ORSAT) Version 7.1. The model is based on laboratory in-situ and residual strength tests of several FRP materials performed during the NASA Orbital Debris Program Office’s Phase II Composite Material Demise test campaign. To test the residual strength of partially charred FRP materials, the authors tested 107 rectangular shaped samples of different thicknesses that were previously exposed to high-enthalpy flow at the University of Texas at Austin’s Inductively Coupled Plasma Torch facility. Tests were performed under normal atmospheric conditions at NASA Johnson Space Center’s Experimental Impact Laboratory using a Chatillon TCD1000 tensile test machine configured with a three-point bending jig. Mean fracture load, residual strength, delamination, and flexural modulus were measured for each test. An engineering model of aeromechanical demise for each material was developed by correlating the measured residual strength of the samples with the duration and magnitude of the applied heat flux and the mass loss and char progression. This model has been implemented in ORSAT 7.1 for the built-in, charring carbon fiber/epoxy and charring glass fiber/epoxy material models. The new model was verified by calculating the demise of hundreds of FRP composite fragments of various shapes and sizes and checking the calculations for consistency, with specific focus on material characterization in one-dimension. Further tests are planned in hypersonic flow facilities to validate the assumptions used in the model.

Priscilla A. Mendoza↗

Sample Polishing Without Epoxy

In recent years, we have received requests for meteorite sample sections to be prepared without using epoxy impregnation or mounting. The reasoning for these requests ranges from potential contamination of analyses from epoxy chemical components to degradation of instrumental vacuum from epoxy outgassing (e.g., SEM, SIMS, EPMA, etc.). An alternative approach that we employ involves sawing off a 1-5 mm thick wafer of the sample. The wafer is ground using silica carbide lapping media wetted with 190 proof ethyl alcohol to make both sides flat and parallel. The sample is then polished on one or both sides using diamond paste or dry diamond powder on a rotating lap wheel until the desired finish is obtained. The sample is cleaned in between steps using 200 proof ethyl alcohol in an ultrasonic cleaner. Friable and altered samples need to have higher thickness in order for polishing to be attempted. Without epoxy to hold the sample together or a glass slide for backing, the sample needs additional material to provide the necessary support structure. The machining steps of this process need to be undertaken at a much slower speed than in traditional thin or thick section preparation.

Meteorite↗

Observation of high-pressure polymorphs in bulk silicon formed at relativistic laser intensities

Silicon polymorphs with exotic electronic and optical properties have recently attracted significant attention due to their wide range of useful band gap characteristics. They are typically formed by static high-pressure techniques, which limits the crystal structures that can be made. This constitutes a major obstacle to study these polymorphs and their incorporation into existing technology. Approaches have attempted to address this shortcoming through using dynamic conditions and chemical precursor materials. Here, we report on an approach to create unusual crystal structures deep in the bulk of a silicon crystal by irradiating it with a laser pulse at ultrarelativistic intensity of up to 7.5 × 10 19 W/ c m 2 . Laser-generated electrons with MeV energy swiftly penetrate the target with speed close to the speed of light and deposit their energy into a large volume across the whole thickness of the sample. The relativistic electron current creates, via branching propagation and ionization, high-energy-density conditions for thermodynamically nonequilibrium phase transformation paths into new crystal polymorphs. X-ray microdiffraction and synchrotron x-ray diffraction analyses indicate, along with conventional dc-Si, the presence of exotic silicon structures in the bulk of the laser intact target volume. These structures are identified as body-centered bc8-Si, rhombohedral r8-Si, hexagonal-diamond hd-Si, and the tetragonal Si-VIII, all phases of Si that have previously been made through static techniques. Additionally, simple-tetragonal st12-Si and body-centered tetragonal bt8-Si were observed along with signatures of not yet identified diffraction spots. Both st12-Si and bt8-Si have only been observed in ultrafast laser microexplosion conditions at much lower laser intensity ∼ 10 14 W/ c m 2 and within a micron-thin surface layer. The findings here are supported by direct observation of nanoparticles with high-resolution transmission electron microscopy and corresponding fast Fourier transform analysis of their interatomic distances. The presented analyses of absorbed laser energy, generation of the MeV electron current, and deposition of energy across the whole target thickness provide a solid basis for drawing the conclusion that the observed silicon polymorphs were produced because of laser-generated high-energy electrons fast-penetrating deeply into the bulk of silicon. In contrast to solid-solid transformations, the plasma-solid transitions offer a paradigm for the creation of exotic, high-energy density materials inside the bulk of the sample by using laser pulses at relativistic intensities. Published by the American Physical Society 2024

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Scale Dependence of Cirrus Horizontal Heterogeneity Effects on TOA Measurements: MODIS Brightness Temperatures in the Thermal Infrared - Part I

This paper presents a study on the impact of cirrus cloud heterogeneities on MODIS simulated thermal infrared (TIR) brightness temperatures (BTs) at the top of the atmosphere (TOA) as a function of spatial resolution from 50 meters to 10 kilometers. A realistic 3-D (three-dimensional) cirrus field is generated by the 3DCLOUD model (average optical thickness of 1.4, cloudtop and base altitudes at 10 and 12 kilometers, respectively, consisting of aggregate column crystals of D (sub eff) equals 20 microns), and 3-D thermal infrared radiative transfer (RT) is simulated with the 3DMCPOL (3-D Monte Carlo Polarized) code. According to previous studies, differences between 3-D BT computed from a heterogenous pixel and 1-D (one-dimensional) RT computed from a homogeneous pixel are considered dependent at nadir on two effects: (i) the optical thickness horizontal heterogeneity leading to the plane-parallel homogeneous bias (PPHB); and the (ii) horizontal radiative transport (HRT) leading to the independent pixel approximation error (IPAE). A single but realistic cirrus case is simulated and, as expected, the PPHB mainly impacts the low-spatial resolution results (above approximately 250 meters), with averaged values of up to 5-7 K (thousand), while the IPAE mainly impacts the high-spatial resolution results (below approximately 250 meters) with average values of up to 1-2 K (thousand). A sensitivity study has been performed in order to extend these results to various cirrus optical thicknesses and heterogeneities by sampling the cirrus in several ranges of parameters. For four optical thickness classes and four optical heterogeneity classes, we have found that, for nadir observations, the spatial resolution at which the combination of PPHB and HRT effects is the smallest, falls between 100 and 250 meters. These spatial resolutions thus appear to be the best choice to retrieve cirrus optical properties with the smallest cloud heterogeneity-related total bias in the thermal infrared. For off-nadir observations, the average total effect is increased and the minimum is shifted to coarser spatial resolutions.

TOA↗

Splat Quenching as a High Throughput Rapid Solidification Testing Method for Developing Additive Manufacturing Alloys

Splat quenching as a high throughput rapid solidification screening tool is evaluated. Samples were made using known alloys (SS316, IN625, Ti-5553) to evaluate and establish the microstructures for a variety of alloy systems as well as the predicted cooling rates. The samples are inductively heated and levitated prior to being struck between two platens that produce a high contact pressure and a thin sample resulting in cooling rates on the order of 10 6 to 10 7 K/s. Process parameters were evaluated with analytical models in addition to numerical simulations to provide an effect of process variables such as substrate material, melt superheat, and platen velocity on the resulting solidification. The splat thickness was found to be controlled by platen velocity, melt superheat, as well as the feedstock volume. The sample thickness is the key controlling factor for varying the average cooling rate experienced by the splat quenched sample. The splat quenching techniques can reach regions of rapid solidification space that meet and exceed laser and electron beam techniques across the sample. In conclusion, the results of the study provide a useful foundation in understanding the splat quenching technique and its potential as a low effort tool to explore rapid solidification effects on alloys.

Alloy Design↗