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14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

In-plane thermal conductivity and the applicability of the Wiedemann–Franz law in dilute AlCu thin films

The Wiedemann–Franz (WF) law correlates heat and charge transport in metals. However, the validity of this correlation remains an open-ended question, especially in the context of inelastic scattering at room temperature. To address this gap in knowledge, we perform independent measurements of the in-plane thermal and electrical conductivities across four AlCu (0.5% Cu) films [thickness (⁠h⁠) ≈ 174, 98, 53, and 24 nm] using optical pump–probe metrologies and four-point probe techniques, respectively. For in-plane thermal conductivity measurements, we utilize time-domain thermoreflectance, in both concentric and beam-offset configurations, and the time-resolved magneto-optic Kerr effect. Our results show that the WF law overpredicts the thermal conductivity by at least ∼10% in all films, thus demonstrating modest deviations in predicted thermal conductivity when applying the WF law to dilute AlCu films. Using infrared variable angle spectroscopic ellipsometry, we demonstrate increased electron scattering rates in the thinnest film (⁠⁠h⁠ ≈ 24 nm), indicating electron-boundary scattering drives the reduction in in-plane thermal conductivity. Furthermore, this is generally an elastic scattering process, which is supported by our thermal conductivity measurements and analysis.

Electrical conductivity↗
NASA NTRS1994

The Low-Lying States of AlCu and AlAg

The singlet and triplet states of AlCu and AlAg below about 32 000/cm are studied using the internally contracted multireference configuration-interaction method. A more elaborate study of the X(sup 1)Sum(sup +) ground state of AlCu is undertaken using extended Gaussian basis sets, including the effect of inner-shell correlation and including a perturbational estimate of relativistic effects. Our best estimate of the spectroscopic constants (r(sub 0), DeltaG(sub 1/2), and D(sub 0)) for the X(sup 1)Sum(sup+) state with the experimental values in parentheses are: 4.416(4.420) a(sub 0), 295 (294) /cm, and 2.318 (2.315) eV. The calculations definitively assign the upper state in the observed transition at 14 892/cm to the lowest (sup 1)Prod state. The calculated spectroscopic constants and radiative lifetime for the (sup 1)Prod state are in good agreement with experiment. The calculations support the tentative assignments of Behm et al. for three band systems observed in the visible region between 25 000 and 28 000 / cm. However, the computed spectroscopic constants are in very poor agreement with those deduced from an analysis of the spectra. Analogous theoretical results for AlAg suggest that the (2)(sup 3)Prod, (3)(sup 3)Prod, and (3)(sup 1)Sum(sup +) states account for the bands observed, but not assigned, by Duncan and co-workers.

Bauschlicher, Charles W., Jr.↗
NASA NTRS2016

Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction.

Ruggles, Timothy↗
DOE OSTI2020

Materials Data on AlCu by Materials Project

CuAl crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Cu sites. In the first Cu site, Cu is bonded in a 6-coordinate geometry to four Cu and six Al atoms. There are two shorter (2.56 Å) and two longer (2.57 Å) Cu–Cu bond lengths. There are four shorter (2.51 Å) and two longer (2.62 Å) Cu–Al bond lengths. In the second Cu site, Cu is bonded in a 11-coordinate geometry to four Cu and seven Al atoms. There are two shorter (2.64 Å) and one longer (2.66 Å) Cu–Cu bond lengths. There are a spread of Cu–Al bond distances ranging from 2.40–2.79 Å. In the third Cu site, Cu is bonded in a 11-coordinate geometry to four Cu and seven Al atoms. There are a spread of Cu–Al bond distances ranging from 2.52–2.68 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 6-coordinate geometry to six Cu atoms. In the second Al site, Al is bonded in a 6-coordinate geometry to six Cu atoms. In the third Al site, Al is bonded in a 8-coordinate geometry to eight Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AlCu by Materials Project

CuAl is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cu is bonded in a body-centered cubic geometry to eight equivalent Al atoms. All Cu–Al bond lengths are 2.60 Å. Al is bonded in a body-centered cubic geometry to eight equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AlCu(WO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(AlCu)6 by Materials Project

Yb(CuAl)6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Yb is bonded in a 12-coordinate geometry to twelve Cu and eight Al atoms. There are four shorter (3.19 Å) and eight longer (3.31 Å) Yb–Cu bond lengths. There are a spread of Yb–Al bond distances ranging from 2.97–3.10 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded to two equivalent Yb, four Cu, and six Al atoms to form a mixture of distorted corner, edge, and face-sharing CuYb2Al6Cu4 cuboctahedra. All Cu–Cu bond lengths are 2.53 Å. There are a spread of Cu–Al bond distances ranging from 2.52–2.65 Å. In the second Cu site, Cu is bonded to two equivalent Yb, four equivalent Cu, and six Al atoms to form a mixture of distorted corner, edge, and face-sharing CuYb2Al6Cu4 cuboctahedra. There are a spread of Cu–Al bond distances ranging from 2.65–2.73 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Yb, six Cu, and three Al atoms. There are one shorter (2.61 Å) and two longer (2.83 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 8-coordinate geometry to one Yb, six Cu, and three Al atoms. There are one shorter (2.64 Å) and two longer (2.88 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Yb, six Cu, and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm(AlCu)6 by Materials Project

Tm(CuAl)6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Tm is bonded in a 12-coordinate geometry to twelve Cu and eight Al atoms. There are four shorter (3.19 Å) and eight longer (3.29 Å) Tm–Cu bond lengths. There are a spread of Tm–Al bond distances ranging from 2.95–3.08 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent Tm, four Cu, and six Al atoms. There are two shorter (2.51 Å) and two longer (2.53 Å) Cu–Cu bond lengths. There are a spread of Cu–Al bond distances ranging from 2.51–2.63 Å. In the second Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent Tm, four equivalent Cu, and six Al atoms. There are a spread of Cu–Al bond distances ranging from 2.61–2.73 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Tm, six Cu, and three Al atoms. There are one shorter (2.62 Å) and two longer (2.83 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 8-coordinate geometry to one Tm, six Cu, and three Al atoms. There are one shorter (2.64 Å) and two longer (2.89 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Tm, six Cu, and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(AlCu)6 by Materials Project

UCu6Al6 crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. U is bonded in a 4-coordinate geometry to eight Cu and twelve Al atoms. There are four shorter (3.04 Å) and four longer (3.31 Å) U–Cu bond lengths. There are eight shorter (3.23 Å) and four longer (3.36 Å) U–Al bond lengths. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Cu, and four equivalent Al atoms. All Cu–Cu bond lengths are 2.70 Å. All Cu–Al bond lengths are 2.43 Å. In the second Cu site, Cu is bonded in a 10-coordinate geometry to one U, three Cu, and six Al atoms. The Cu–Cu bond length is 2.64 Å. There are a spread of Cu–Al bond distances ranging from 2.62–2.73 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Cu, and six Al atoms. There are two shorter (2.51 Å) and four longer (2.61 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, six Cu, and four Al atoms. There are one shorter (2.76 Å) and one longer (3.00 Å) Al–Al bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(AlCu)6 by Materials Project

Gd(CuAl)6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to twelve Cu and eight Al atoms. There are four shorter (3.22 Å) and eight longer (3.31 Å) Gd–Cu bond lengths. There are a spread of Gd–Al bond distances ranging from 2.98–3.10 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent Gd, four Cu, and six Al atoms. There are two shorter (2.53 Å) and two longer (2.54 Å) Cu–Cu bond lengths. There are a spread of Cu–Al bond distances ranging from 2.53–2.66 Å. In the second Cu site, Cu is bonded to two equivalent Gd, four equivalent Cu, and six Al atoms to form a mixture of distorted corner, edge, and face-sharing CuGd2Al6Cu4 cuboctahedra. There are a spread of Cu–Al bond distances ranging from 2.65–2.74 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Gd, six Cu, and three Al atoms. There are one shorter (2.63 Å) and two longer (2.84 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 8-coordinate geometry to one Gd, six Cu, and three Al atoms. There are one shorter (2.64 Å) and two longer (2.90 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Gd, six Cu, and four Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Lu(AlCu)6 by Materials Project

Lu(CuAl)6 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Lu is bonded in a 12-coordinate geometry to twelve Cu and eight Al atoms. There are four shorter (3.19 Å) and eight longer (3.29 Å) Lu–Cu bond lengths. There are a spread of Lu–Al bond distances ranging from 2.95–3.08 Å. There are two inequivalent Cu sites. In the first Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent Lu, four Cu, and six Al atoms. There are two shorter (2.51 Å) and two longer (2.53 Å) Cu–Cu bond lengths. There are a spread of Cu–Al bond distances ranging from 2.52–2.63 Å. In the second Cu site, Cu is bonded in a 12-coordinate geometry to two equivalent Lu, four equivalent Cu, and six Al atoms. There are a spread of Cu–Al bond distances ranging from 2.60–2.73 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Lu, six Cu, and three Al atoms. There are one shorter (2.63 Å) and two longer (2.83 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 8-coordinate geometry to one Lu, six Cu, and one Al atom. The Al–Al bond length is 2.64 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to two equivalent Lu, six Cu, and two equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Using θ' interfaces as templates for planar L1 2 precipitation in AlCuMnZr alloys

Controlled Mn and Zr additions to Al-Cu alloys have allowed for the improved retention of mechanical properties after extended 350°C exposures by stabilizing the main strengthening θ' (Al 2 Cu) phase. Ultimately, θ'/L1 2 (Al 3 Zr) co-precipitate formation stabilizes θ' most effectively; however, Zr diffuses sluggishly and has low solubility in aluminum castings. Increasing the Zr segregation rate would allow for faster and more effective θ'/L1 2 co-precipitation. It is demonstrated that the Zr segregation rate is faster when the Zr matrix content is higher. A much higher Zr matrix content was achieved by rapid cooling during additive manufacturing (AM) that produces θ'/L1 2 co-precipitation faster, which is shown by scanning transmission electron microscopy and atom probe tomography experiments. It was also found that Zr continuously segregates to θ' interfaces up to the most aggressive heat treatment studied such that planar L1 2 precipitates remain after the metastable θ' dissolves. In this manner, we demonstrate that θ' coherent interfaces serve as perfect templates to form stable planar L1 2 precipitates that can provide strength at higher temperatures than traditional θ' strengthened AlCu alloys. This work introduces an alloy design strategy that uses metastable precipitates to quickly nucleate and grow co-precipitates with a desired geometry that contain slow diffusing elements. These ideas can be applied to engineer more heat resistant alloys by taking advantage of high solute matrix contents enabled by rapid cooling during additive manufacturing.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Molecular Spectroscopy by Ab Initio Methods

Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point where these methods can be used to provide accurate spectroscopic constants for small molecules; this will be illustrated with several examples. We will show how ab initio calculations where used to identify the Hermann infrared system in N2 and two band systems in CO. The identification of all three of these band systems relied on very accurate calculations of quintet states. The analysis of the infrared spectra of cool stars requires knowledge of the intensity of vibrational transitions in SiO for high nu and J levels. While experiment can supply very accurate dipole moments for nu = 0 to 3, this is insufficient to construct a global dipole moment function. We show how theory, combined by the experiment, can be used to generate the line intensities up to nu = 40 and J = 250. The spectroscopy of transition metal containing systems is very difficult for both theory and experiment. We will discuss the identification of the ground state of Ti2 and the spectroscopy of AlCu as examples of how theory can contribute to the understanding of these complex systems.

Bauschlicher, Charles W., Jr.↗
NASA NTRS2003

Characterization of Al-Cu-Mg-Ag Alloy RX226-T8 Plate

Aluminum-copper-magnesium-silver (Al-Cu-Mg-Ag) alloys that were developed for thermal stability also offer attractive ambient temperature strength-toughness combinations, and therefore, can be considered for a broad range of airframe structural applications. The current study evaluated Al-Cu-Mg-Ag alloy RX226-T8 in plate gages and compared performance with sheet gage alloys of similar composition. Uniaxial tensile properties, plane strain initiation fracture toughness, and plane stress tearing resistance of RX226-T8 were examined at ambient temperature as a function of orientation and thickness location in the plate. Properties were measured near the surface and at the mid-plane of the plate. Tensile strengths were essentially isotropic, with variations in yield and ultimate tensile strengths of less than 2% as a function of orientation and through-thickness location. However, ductility varied by more than 15% with orientation. Fracture toughness was generally higher at the mid-plane and greater for the L-T orientation, although the differences were small near the surface of the plate. Metallurgical analysis indicated that the microstructure was primarily recrystallized with weak texture and was uniform through the plate with the exception of a fine-grained layer near the surface of the plate. Scanning electron microscope analysis revealed Al-Cu-Mg second phase particles which varied in composition and were primarily located on grain boundaries parallel to the rolling direction. Fractography of toughness specimens for both plate locations and orientations revealed that fracture occurred predominantly by transgranular microvoid coalescence. Introduction High-strength, low-density Al-Cu-Mg-Ag alloys were initially developed to replace conventional 2000 (Al-Cu-Mg) and 7000 (Al-Zn-Cu-Mg) series aluminum alloys for aircraft structural applications [1]. During the High Speed Civil Transport (HSCT) program, improvements in thermal stability were demonstrated for candidate aircraft wing and fuselage skin materials through the addition of silver to Al-Cu-Mg alloys based on Al 2519 chemistry [2]. Thermal stability of the resulting Al-Cu-Mg-Ag alloys, C415-T8 and C416-T8, was due to co-precipitation of the thermally stable . (AlCu) and ' (Al2Cu) strengthening phases [1-4]. The strength and toughness behavior was investigated for these alloys produced as 0.090-inch thick rolled sheet in the T8 condition and after various thermal exposures. The mechanical properties were shown to be competitive with conventional aircraft alloys, 2519-T8 and 2618-T8 [2]. During the Integral Airframe Structure (IAS) program, advanced aluminum alloys were examined for use in an integrally stiffened airframe structure where the skin and stiffeners would be machined from plate and extruded frames would be mechanically attached (see Figure 1) [5]. Advantages of integrally stiffened structure include reduced part count, and reduced assembly times compared to conventional built-up airframe structure. The near-surface properties of a thick plate are of significance for a machined integrally stiffened airframe structure since this represents the skin location. Properties measured at the mid-plane of the plate are more representative of the stiffener web. RX226 was developed to exploit strength-toughness improvements and thermal stability benefits of Al-Cu-Mg-Ag alloys in plate gages. This study evaluated the microstructure and properties of three gages of plate produced in the T8 condition.

Lach, Cynthia L.↗