Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Al2Cu”

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.

30 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Lu(Al2Cu)4 by Materials Project

Lu(CuAl2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Lu is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Lu–Cu bond lengths are 3.37 Å. There are four shorter (3.06 Å) and eight longer (3.19 Å) Lu–Al bond lengths. Cu is bonded in a 12-coordinate geometry to two equivalent Lu, two equivalent Cu, and eight Al atoms. Both Cu–Cu bond lengths are 2.55 Å. There are four shorter (2.57 Å) and four longer (2.69 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Lu, four equivalent Cu, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.84 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Lu, four equivalent Cu, and four equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Er(Al2Cu)4 by Materials Project

Al8Cu4Er crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Er is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Er–Cu bond lengths are 3.36 Å. There are four shorter (3.06 Å) and eight longer (3.19 Å) Er–Al bond lengths. Cu is bonded in a 12-coordinate geometry to two equivalent Er, two equivalent Cu, and eight Al atoms. Both Cu–Cu bond lengths are 2.55 Å. There are four shorter (2.56 Å) and four longer (2.69 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Er, four equivalent Cu, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.69–2.83 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Er, four equivalent Cu, and six Al atoms. Both Al–Al bond lengths are 2.71 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on U(Al2Cu)4 by Materials Project

UCu4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U is bonded in a distorted square co-planar geometry to four equivalent Cu and sixteen Al atoms. All U–Cu bond lengths are 3.04 Å. There are eight shorter (3.33 Å) and eight longer (3.36 Å) U–Al bond lengths. Cu is bonded in a 10-coordinate geometry to one U, one Cu, and eight Al atoms. The Cu–Cu bond length is 2.62 Å. There are a spread of Cu–Al bond distances ranging from 2.70–2.91 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 four shorter (2.57 Å) and two longer (2.70 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent U, four equivalent Cu, and six Al atoms. Both Al–Al bond lengths are 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Yb(Al2Cu)4 by Materials Project

YbCu4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Yb is bonded in a 12-coordinate geometry to eight equivalent Cu and twelve Al atoms. All Yb–Cu bond lengths are 3.38 Å. There are four shorter (3.07 Å) and eight longer (3.21 Å) Yb–Al bond lengths. Cu is bonded to two equivalent Yb, two equivalent Cu, and eight Al atoms to form a mixture of distorted edge, corner, and face-sharing CuYb2Al8Cu2 cuboctahedra. Both Cu–Cu bond lengths are 2.56 Å. There are four shorter (2.57 Å) and four longer (2.70 Å) Cu–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Yb, four equivalent Cu, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.83 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Yb, four equivalent Cu, and six Al atoms. Both Al–Al bond lengths are 2.74 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Dislocation-θ' (Al2Cu) interactions during creep deformation of an Al-Cu alloy

While precipitate-dislocation interactions are well-understood for Al-Cu alloys in tension, creep behavior has seen far less study. New, thermally-stabilized Al-Cu alloys have θ' (Al 2 Cu) as strengthening precipitates that remain stable up to 300 °C (~60% of the melting temperature) and higher, where creep becomes essential to the mechanical behavior. This investigation identifies the precipitate-dislocation interactions in such an Al-Cu alloy using in-situ neutron diffraction and scanning transmission electron microscopy. Significant load transfer to the θ' precipitates occurs, which can be attributed to dislocation loops on the interfaces of θ' and the Al matrix. Thus, Orowan looping is identified to be the primary activity for precipitate-dislocation interactions. As Orowan looping and load transfer are associated with significant strain hardening, these results explain the excellent creep resistance seen in this alloy, and provide insights into the design of precipitation strengthened alloys with superior creep performance.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Cavitation-resistant intergranular precipitates enhance creep performance of θ'-strengthened Al-Cu based alloys

Tensile and compressive creep properties of a quaternary Al-Cu-Mn-Zr (ACMZ) alloy and its commercial counterpart (Al-Cu-Mn-Zr with Ni, Co and Sb additions, RR350) are investigated at 300°C. At low stresses up to 30 MPa where diffusional creep dominates, creep resistance is the same in tension and compression and RR350 deforms more slowly than ACMZ, consistent with RR350 alloy's larger linear fraction of intergranular precipitates (Al7Cu2(NiFe) and Al9FeNi for RR350 vs. θ-Al2Cu for ACMZ) and a reduced fraction of precipitate-free zones near grain boundaries. At stresses between 30 and 80 MPa, dislocation creep with a stress exponent n ~ 3 becomes rate-limiting in compression, which is expected to be controlled by θ' precipitates within the grain bulk. By contrast, in tension, enhanced creep rate and higher apparent stress exponents are measured, consistent with cavitation at intergranular precipitates becoming increasingly dominant as the stress increases. In the dislocation creep regime, RR350 alloy is again more creep resistant than ACMZ alloy, which is related to three mechanisms (i) a reduced fraction of softer precipitate-free zones, (ii) more effective load transfer to intergranular precipitates, and (iii) reduced cavitation. A model for cavitation is applied to calculate tensile creep rates from compressive creep rates and the model successfully predicts the improved tensile creep resistance of the RR350 alloy. Overall, the present investigation underscores the importance of intergranular grain boundary precipitates, in addition to strengthening θ' precipitates, in enhancing the creep resistance of Al-Cu alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Creep deformation and cavitation in an additively manufactured Al-8.6Cu-0.4Mn-0.9Zr (wt%) alloy

Creep deformation and cavitation were investigated at 300 ºC in both tension and compression for an additively manufactured Al-8.6Cu-0.5Mn-0.9Zr (wt%) alloy in the as-fabricated state and after various aging treatments (aging at 300 °C/200 h or 350 °C/24 h and overaging at 400 °C/200 h). Creep mechanisms at 300 °C were determined by relating the measured creep response to corresponding microstructural and X-ray computed tomography observations. In compression, alloys in the as-fabricated and two aging conditions exhibited similarly high creep resistance. Overaging (400 °C/200 h) led to substantial coarsening of intragranular θ-Al2Cu precipitates and an expected drop in their Orowan strengthening contribution. In tension, minimum strain rates comparable to those in compression were obtained at any given stress; however, upon accumulation of some plastic strain in the matrix, creep cavities started to form, leading to accelerated tertiary stage creep deformation and rupture. Cavitation occurred exclusively along melt pool boundaries due to locally enhanced diffusion enabled by (i) large grain-boundary area in adjacent fine-grained zones and (ii) localization of creep strain in nearby heat-affected zones. Although cavity growth was initially diffusion-controlled, its rate was determined by matrix creep rate, consistent with constrained cavity growth mechanisms. This study reveals how microstructural complexities induced by the additive manufacturing process affect the creep and cavitation behavior of Al-Cu-Mn-Zr alloys. The underlying creep and cavitation mechanisms uncovered in this study point to pathways that improve the high-temperature properties of additively manufactured alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Characterization of electromigration-induced short-range stress development in Al(0.25 at. % Cu) conductor line

Scanning x-ray microbeam topography and fluorescence experiments were conducted in situ to study the electromigration behavior of a 0.5 μm thick, 10 μm wide, and 200 μm long Al(0.25 at. % Cu) conductor line with 1.5 μm-thick SiO2 passivation on a single crystal Si substrate. The strain sensitivity of x-ray topography measurement allowed detailed examination of the electromigration-induced stress distribution and evolution in the conductor line in response to the depletion of Cu solute early in the electromigration process. Upon electromigration at 0.4 MA/cm2 and 303 °C, a short-range stress gradient was quickly induced by Al migration in the Cu-depleted cathode region to counteract further Al flow. The stress gradient was fully developed during the 5.3 h incubation time, extending over the critical Blech length of about 66 μm from the cathode end. Plastic deformation then occurred at the downstream end of the Cu-depleted region. The preferential electromigration of Cu did not cause detectable stress change outside the Cu-depleted region, except for the significant stress development from the Al2Cu precipitation at the anode end which appeared to initiate the fracture in the passivation. Preliminary finite difference modeling was undertaken to simulate the experimental observations, from which important parameters dictating electromigration in Al(Cu) line were extracted: an apparent effective valence of −5.6 and −1.9 for Cu and Al in Al(Cu), respectively, and a critical Cu concentration of 0.16 at. % above which Al grain boundary diffusion is effectively blocked.

Physics↗
DOE OSTI2024

The many faces of θ' -Al 2 Cu precipitates: Energetics of pristine and solute segregated Al/ θ' semi-coherent interfaces

θ'-Al 2 Cu precipitates in Al-Cu alloys have various distorted octagon shapes, which can be explained by the competition between {100} and {110} type semi-coherent interfaces with the Al matrix. While most prior studies on the semi-coherent Al/θ' interfaces have focused on the {100} orientation, little is known about the {110} interface. We have investigated the energetics of pristine and solute-segregated {110} semi-coherent Al/θ' interfaces with advanced characterization and first-principles studies. We report interfacial, strain, and solute segregation energetics of the {110} Al/θ' semi-coherent interface for 39 elements and compared them with previously reported values of the {100} interface. We discuss the atomic features and atomic local structures to identify similarities and differences between the two types of Al/θ' semi-coherent interfaces. Here, the isotropy in pristine Al/θ' semi-coherent interfacial energy and the anisotropy resulting from solute segregation provide insight into the formation of different types of θ' precipitate “faces” reported in the literature.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Deformation behavior of nanoscale Al–Al 2 Cu eutectics studied by in situ micropillar compression

We report deformation behavior of nanoscale laser processed Al–Al 2 Cu eutectics at room temperature is characterized through in situ micro-pillar compression testing in a scanning transmission microscope. Interlamellar spacing of Al–Al 2 Cu eutectics varies from hundreds of nanometers to 20 nm. Three different sizes of micro-pillars are fabricated in order to study the deformation behaviors of single colony and multiple colonies, corresponding to the single crystal and polycrystal respectively. For single colonies, lamellar orientations parallel, normal or inclined to the loading direction were tested. The main findings are: 1) the plasticity mechanisms strongly depend on loading orientation: buckling and kinking in the parallel-loaded eutectics, planar sliding along Al–Al 2 Cu lamellar interfaces in the incline-loaded eutectics and localized shearing in the normal-loaded eutectics. 2) the incline-loaded eutectics exhibits the lowest compression flow strength, and the normal-loaded eutectics has the highest compression flow strength. 3) with decreasing inter-lamellar spacing, the strength increases and plasticity is uniformly distributed, as opposed to shear localization. Highest compressive plasticity is observed in polycrystalline eutectics with an ensemble of lamellar orientations with ~20 nm average spacing: 17.9% at flow stress of 1.63 GPa, and degenerate, bimodal morphology: 11.1% at flow stress of 1.36 GPa.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of grain-boundary θ-Al 2 Cu precipitates on tensile and compressive creep properties of cast Al–Cu–Mn–Zr alloys

Tensile and compressive creep tests were performed at 300 °C on high-temperature Al–Cu–Mn–Zr (ACMZ) alloys with 6 wt% Cu (6Cu) and 9 wt% Cu (9Cu) to evaluate the effect on creep properties of micron-size θ-Al 2 Cu intergranular precipitates. For compressive creep, the increased volume fraction of θ-precipitates at grain boundaries (from ~0.7% in 6Cu to ~ 6% in 9Cu) does not affect deformation rates across the investigated stress range of 15–110 MPa, consistent with creep being controlled by submicron θ'-Al 2 Cu precipitates within grains, whose size and fractions are the same in both alloys. In contrast, for tensile creep, 9Cu creeps faster than 6Cu at stresses above 20 MPa, and this difference increases with the stress level. Additionally, this discrepancy between tensile and compressive creep behavior is explained by cavitation during tensile creep, which is favored by higher volume fraction and larger size of intergranular θ precipitates in 9Cu. Conversely, larger precipitates impede cavity linkage resulting in improved creep ductility of 9Cu as compared to 6Cu at 300 °C.

36 MATERIALS SCIENCE↗