Search NASA⌕ Search

SEARCH · Search NASA

Results for “EUTECTIC ALLOY”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Structural evolution of low-temperature liquid GaIn eutectic alloy

Structural changes of liquid Galn eutectic alloy upon cooling from about 373 K to 242 K are studied by using in situ synchrotron radiation X-ray diffraction (XRD) combined with the ab initio molecular dynamics simulations (AIMD). The experimental and theoretical results show that no abnormal structural change is observed in the supercooled liquid region prior to crystallization. The XRD data exhibit that the liquid can crystallize into a mixture of orthorhombic Ga-I and body-centered tetragonal (bct)-In phases. Also, the AIMD calculations simulate the solidification process, forming a bct-like structure locally similar to bct-Ga-III and bct-In phases. The aggregation of In atoms forms In-rich zones, acting as the processor of crystallization. Our results provide an in-depth understanding of liquid Galn alloys and will trigger more interests to other metallic liquids. (C) 2019 Elsevier B.V. All rights reserved.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Macrosegregation in undercooled Pb-Sn eutectic alloys

A novel technique resulting in large undercoolings in bulk samples (23g) of lead-tin eutectic alloy is described. Samples of eutectic composition were processed with undercoolings ranging from 4 to 20 K and with cooling rates varying between 0.04 to 4 K/sec. The final macrostructure of undercooled samples depends on both the initial undercooling of the melt and the cooling rate. Gravity-driven segregation is found to increase with increasing undercooling. A eutectic Pb-Sn alloy undercooled at 20 K and cooled at 4 K/sec had a composition of about Pb-72 wt pct Sn at the top and 55 pct Sn at the bottom. Macrosegregation in these undercooled lead-tin eutectic alloys is shown to be primarily due to a sink/float mechanism caused by the difference in density of the solid and liquid phases and the undercooling and nucleation behavior of the alloy.

De Groh, H. C., III↗
DOE OSTI2024

Strong‐Yet‐Ductile Eutectic Alloys Employing Cocoon‐Like Nanometer‐Sized Dislocation Cells

Abstract Eutectic alloys (EAs) with superior fluidity are known to be the easiest to cast into high‐quality ingots, making them the alloys of choice for making large‐sized structural parts. However, conventional EAs (CEAs) have never reached strength–ductility combinations on par with the best in other alloy categories. Via thermomechanical processing of cast Ni‐32.88wt%Fe‐9.53wt%Al CEAs, a cocoon‐like nano‐meshed (as fine as 26 nm) network of dislocations (CNN‐D) is produced via recovery annealing, through the rearrangement of cold‐work‐accumulated dislocations anchored by dense pre‐existing nanoprecipitates. In lieu of traditional plasticity mechanisms, such as TWIP and TRIP, the CNN‐D is particularly effective in eutectic lamellae with alternating phases, as it instigates nanometer‐spaced planar slip bands that not only dynamically refine the microstructure but also transmit from the FCC (face‐centered‐cubic) layers into the otherwise brittle B2 layers. These additional mechanisms for strengthening and strain hardening sustain stable tensile flow, resulting in a striking elevation of both strength and ductility to outrank not only all previous CEAs, but also the state of the art—additively manufactured eutectic high‐entropy alloys. The CNN‐D thus adds a novel microstructural strategy for performance enhancement, especially for compositionally complex alloys that increasingly make use of nanoprecipitates or local chemical order.

Chemistry↗
DOE OSTI2025

Leveraging Artificial Intelligence to Predict Novel Eutectic Alloys

The goal of this project was to train an artificial neural network (ANN) to predict the fractional composition and melting point of eutectic alloys using fundamental atomic properties as inputs. The fundamental properties considered include atomic number, atomic weight, atomic radius, valence electron concentration, electronegativity, and electron affinity. The project involved several phases, starting with data preparation, where phase diagram data was harvested from the ASM International database. Approximately 1300 binary eutectics were collected and cleaned to ensure relevance and accuracy. A regression model was selected for training, utilizing a rectified linear unit as the activation function. Various model configurations were evaluated for predictive accuracy, with validation techniques employed to ensure robustness. The model demonstrated predictive capabilities above random guessing and was able to achieve up to 11% accuracy under certain conditions. An ablative test identified atomic radius and valence electron concentration as critical inputs for model performance. Incorporating the melting point of atomic constituents improved accuracy significantly, although ultimately the model’s predictive capability still fell short of the 80% target. This report details the methodology, results, and implications of the research, contributing to the understanding of employing artificial intelligence to predict the phase transition behavior of eutectic alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Liquid-to-liquid crossover in the GaIn eutectic alloy

Liquid-liquid crossover is promising and closely related to the atomic dynamics during heating and cooling processes. Here we reveal a reversible structural crossover in the liquid Ga85.8In14.2 eutectic alloys by using in situ synchrotron x-ray diffraction and ab initio molecular dynamics simulation. A kink always appears on the temperature dependent behaviors of density, ratio of the second peak position to the first in the pair correlation function, coordination number, heat capacity, free energy, and atomic diffusivity in the temperature range of about 400–550 K. It is likely ascribed to atomic rearrangements of Ga and In atoms from a relative random packing at high temperatures to a relative nonuniform packing at low temperatures, in which In atoms prefer to have more In neighbors. This observation will promote more understanding of the liquid structure of eutectic alloys

Yu, Q.↗
NASA NTRS1988

Microstructure Of MnBi/Bi Eutectic Alloy

Collection of three reports describes studies of directional solidification of MnBi/Bi eutectic alloy. Two of the reports, "Influence of Convection on Lamellar Spacing of Eutectics" and "Influence of Convection on Eutectic Microstructure," establish theoretical foundation for remaining document. Reports seek to quantify effect of convection on concentration field of growing lamellar eutectic. Remaining report, "Study of Eutectic Formation," begins by continuing theoretical developments. New technique under development by one of the authors helps to reveal three-dimensional microstructures of alloys.

Wilcox, William R.↗
NASA NTRS1975

Resistance of a gamma/gamma prime - delta directionally solidified eutectic alloy to recrystallization

The lamellar directionally solidified nickel-base eutectic alloy gamma/gamma prime-delta has potential as an advanced turbine blade material. The microstructural stability of this alloy was investigated. Specimens were plastically deformed by uniform compression or Brinell indentation, then annealed between 705 and 1120 C. Microstructural changes observed after annealing included gamma prime coarsening, pinch-off and spheroidization of delta lamellae, and the appearance of an unidentified blocky phase in surface layers. All but the first of these was localized in severely deformed regions, suggesting that microstructural instability is not a serious problem in the use of this alloy.

Tewari, S. N.↗
NASA NTRS1976

Alloy and structural optimization of a directionally solidified lamellar eutectic alloy

Mechanical property characterization tests of a directionally solidified Ni-20 percent Cb-2.5 percent Al-6 percent Cr cellular eutectic turbine blade alloy demonstrated excellent long time creep stability and indicated intermediate temperature transverse tensile ductility and shear strength to be somewhat low for turbine blade applications. Alloy and structural optimization significantly improves these off-axis properties with no loss of longitudinal creep strength or stability. The optimized alloy-structure combination is a carbon modified Ni-20.1 percent Cb-2.5 percent Al-6.0 percent Cr-0.06 percent C composition processed under conditions producing plane front solidification and a fully-lamellar microstructure. With current processing technology, this alloy exhibits a creep-rupture advantage of 39 C over the best available nickel base superalloy, directionally solidified MAR M200+ Hf. While improved by about 20 percent, shear strength of the optimized alloy remains well below typical superalloy values.

Sheffler, K. D.↗
NASA NTRS1976

Heat treating of a lamellar eutectic alloy (gamma/gamma prime + delta)

Eutectic superalloys are being developed at several laboratories for application as aircraft gas turbine airfoils. One such alloy was subjected to several heat treatments to determine if its mechanical properties could be improved. It was found that by partially dissolving the alloy at 1210 C and then aging at 900 C the tensile strength can be increased about 12 percent at temperatures up to 900 C. At 1040 C no change in tensile strength was observed. Times to rupture were measured between 760 and 1040 C and were essentially the same or greater than for as-grown material. Tensile and rupture ductility of the alloy are reduced by heat treatment. Photographs of the microstructure are shown.

Tewari, S. N.↗
NASA NTRS1976

Heat treating of a lamellar eutectic alloy /gamma/gamma prime + delta/

Eutectic superalloys are being developed at several laboratories for application as aircraft gas turbine airfoils. One such alloy gamma/gamma prime + delta was subjected to several heat treatments to determine if its mechanical properties could be improved. It was found that by partially dissolving the gamma prime at 1210 C and then aging at 900 C, the tensile strength can be increased about 12 per cent at temperatures up to 900 C. At 1040 C, no change in tensile strength was observed. Times to rupture were measured between 760 and 1040 C and were essentially the same or greater than for as-grown material. Tensile and rupture ductility of the alloy were reduced by heat treatment.

Tewari, S. N.↗