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9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Intermetallic particle heterogeneity controls shear localization in high-strength nanostructured Al alloys

The mechanical behavior of two nanocrystalline Al alloys, Al-Mg-Y and Al-Fe-Y, is investigated with in-situ micropillar compression testing. Both alloys were strengthened by a hierarchical microstructure including grain boundary segregation, nanometer-thick amorphous complexions, carbide nanorod precipitates with sizes of a few nanometers, and submicron-scale intermetallic particles. The maximum yield strength of the Al-Mg-Y system is measured to be 950 MPa, exceeding that of the Al-Fe-Y system (680 MPa), primarily due to a combination of more carbide nanorods and more amorphous complexions. Both alloys exhibited yield strengths much higher than those of commercial Al alloys, and therefore have great potential for structural applications. However, some micropillar specimens were observed to plastically soften through shear banding. Post-mortem investigation revealed that intermetallic-free deformation pathways of a few micrometers in length were responsible for this failure. Further characterization showed significant grain growth within the shear band. The coarsened grains maintained the same orientation with each other, pointing to grain boundary mechanisms for plastic flow, specifically grain rotation and/or grain boundary migration. Here, the presence of intermetallic particles makes it difficult for both matrix and intermetallic grains to rotate into the same orientation due to the different lattice parameters and slip systems. Therefore, we are able to conclude that a uniform distribution of intermetallic particles with an average spacing less than the percolation length of shear localization can effectively prevent the maturation of shear bands, offering a design strategy for high-strength nanocrystalline Al alloys with both high strength and stable plastic flow.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Bulk nanocrystalline Al alloys with hierarchical reinforcement structures via grain boundary segregation and complexion formation

Grain size engineering, particularly reducing grain size into the nanocrystalline regime, offers a promising pathway to further improve the strength-to-weight ratio of Al alloys. Unfortunately, the fabrication of nanocrystalline metals often requires non-equilibrium processing routes, which typically limit the specimen size and require large energy budgets. In this study, multiple dopant elements in ternary Al alloys are deliberately selected to enable segregation to the grain boundary region and promote the formation of amorphous complexions. Three different fully dense bulk nanocrystalline Al alloys (Al-Mg-Y, Al-Fe-Y, and Al-Ni-Y) with small grain sizes were successfully fabricated using a simple powder metallurgy approach, with full densification connected directly to the onset of amorphous complexion formation. All the compositions demonstrate densities above 99% with grain sizes <60 nm following consolidation via hot pressing at 585 °C. The very fine grain structure results in excellent mechanical properties, as evidenced by nanoindentation hardness values in the range of 2.2-2.8 GPa. Detailed microstructural characterization verifies the segregation of all dopant species to grain boundaries as well as the formation of amorphous complexions, which suggests their influential role in aiding effective consolidation and endowing thermal stability in the alloys. Moreover, nanorods with a core-shell structure are also observed at the grain boundaries, which likely contribute to the stabilization of the grain structure while also strengthening the materials. Lastly, intermetallic particles with sizes of hundreds of nanometers form in all systems. As a whole, the results presented here demonstrate a general alloy design strategy of segregation and boundary evolution pathway that enables the fabrication of multiple nanocrystalline Al alloys with hierarchical microstructures and improved performance.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Al5Fe)2 by Materials Project

YFe2Al10 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Y is bonded in a 10-coordinate geometry to four equivalent Fe and sixteen Al atoms. All Y–Fe bond lengths are 3.41 Å. There are a spread of Y–Al bond distances ranging from 3.10–3.65 Å. Fe is bonded in a 10-coordinate geometry to two equivalent Y and ten Al atoms. There are a spread of Fe–Al bond distances ranging from 2.51–2.71 Å. There are five inequivalent Al sites. In the first Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.59–2.82 Å. In the second Al site, Al is bonded to one Y, two equivalent Fe, and nine Al atoms to form a mixture of distorted corner and face-sharing AlYAl9Fe2 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.70–3.00 Å. In the third Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.56–2.74 Å. In the fourth Al site, Al is bonded in a 2-coordinate geometry to one Y, two equivalent Fe, and eight Al atoms. There are one shorter (2.69 Å) and two longer (2.78 Å) Al–Al bond lengths. In the fifth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Al2Fe)4 by Materials Project

YFe4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to eight equivalent Fe and twelve Al atoms. All Y–Fe bond lengths are 3.32 Å. There are four shorter (2.96 Å) and eight longer (3.16 Å) Y–Al bond lengths. Fe is bonded in a 12-coordinate geometry to two equivalent Y, two equivalent Fe, and eight Al atoms. Both Fe–Fe bond lengths are 2.51 Å. There are four shorter (2.52 Å) and four longer (2.63 Å) Fe–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Y, four equivalent Fe, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.72–2.80 Å. In the second Al site, Al is bonded in a 12-coordinate geometry to two equivalent Y, four equivalent Fe, and six Al atoms. Both Al–Al bond lengths are 2.72 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2Al3Fe by Materials Project

Y2FeAl3 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to four equivalent Y, three equivalent Fe, and nine equivalent Al atoms. There are one shorter (3.31 Å) and three longer (3.35 Å) Y–Y bond lengths. All Y–Fe bond lengths are 3.22 Å. There are three shorter (3.16 Å) and six longer (3.21 Å) Y–Al bond lengths. Fe is bonded to six equivalent Y and six equivalent Al atoms to form FeY6Al6 cuboctahedra that share corners with six equivalent FeY6Al6 cuboctahedra, corners with twelve equivalent AlY6Al4Fe2 cuboctahedra, edges with six equivalent FeY6Al6 cuboctahedra, and faces with eighteen equivalent AlY6Al4Fe2 cuboctahedra. All Fe–Al bond lengths are 2.71 Å. Al is bonded to six equivalent Y, two equivalent Fe, and four equivalent Al atoms to form AlY6Al4Fe2 cuboctahedra that share corners with four equivalent FeY6Al6 cuboctahedra, corners with fourteen equivalent AlY6Al4Fe2 cuboctahedra, edges with six equivalent AlY6Al4Fe2 cuboctahedra, faces with six equivalent FeY6Al6 cuboctahedra, and faces with twelve equivalent AlY6Al4Fe2 cuboctahedra. All Al–Al bond lengths are 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(AlFe2)4 by Materials Project

Y(Fe2Al)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to sixteen Fe and four equivalent Al atoms. There are eight shorter (3.16 Å) and eight longer (3.25 Å) Y–Fe bond lengths. All Y–Al bond lengths are 2.93 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Y, six Fe, and four equivalent Al atoms to form a mixture of distorted edge, face, and corner-sharing FeY2Al4Fe6 cuboctahedra. There are four shorter (2.46 Å) and two longer (2.47 Å) Fe–Fe bond lengths. All Fe–Al bond lengths are 2.59 Å. In the second Fe site, Fe is bonded in a 12-coordinate geometry to two equivalent Y, six Fe, and four equivalent Al atoms. Both Fe–Fe bond lengths are 2.80 Å. There are two shorter (2.62 Å) and two longer (2.65 Å) Fe–Al bond lengths. Al is bonded in a 10-coordinate geometry to one Y, eight Fe, and one Al atom. The Al–Al bond length is 2.63 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on YAlFe by Materials Project

AlFeY crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to six equivalent Fe and six equivalent Al atoms. There are two shorter (3.03 Å) and four longer (3.22 Å) Y–Fe bond lengths. There are four shorter (3.13 Å) and two longer (3.18 Å) Y–Al bond lengths. Fe is bonded to six equivalent Y, two equivalent Fe, and four equivalent Al atoms to form FeY6Al4Fe2 cuboctahedra that share corners with eight equivalent AlY6Al2Fe4 cuboctahedra, corners with ten equivalent FeY6Al4Fe2 cuboctahedra, edges with six equivalent FeY6Al4Fe2 cuboctahedra, faces with six equivalent FeY6Al4Fe2 cuboctahedra, and faces with twelve equivalent AlY6Al2Fe4 cuboctahedra. Both Fe–Fe bond lengths are 2.67 Å. All Fe–Al bond lengths are 2.67 Å. Al is bonded to six equivalent Y, four equivalent Fe, and two equivalent Al atoms to form AlY6Al2Fe4 cuboctahedra that share corners with eight equivalent FeY6Al4Fe2 cuboctahedra, corners with ten equivalent AlY6Al2Fe4 cuboctahedra, edges with six equivalent AlY6Al2Fe4 cuboctahedra, faces with six equivalent AlY6Al2Fe4 cuboctahedra, and faces with twelve equivalent FeY6Al4Fe2 cuboctahedra. Both Al–Al bond lengths are 2.75 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2Al3Fe14 by Materials Project

Y2Fe14Al3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded in a 6-coordinate geometry to eighteen Fe atoms. There are a spread of Y–Fe bond distances ranging from 2.90–3.27 Å. In the second Y site, Y is bonded in a 8-coordinate geometry to fourteen Fe and six equivalent Al atoms. There are a spread of Y–Fe bond distances ranging from 2.97–3.16 Å. All Y–Al bond lengths are 3.21 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded in a 5-coordinate geometry to one Y, ten Fe, and three equivalent Al atoms. There are a spread of Fe–Fe bond distances ranging from 2.27–2.88 Å. All Fe–Al bond lengths are 2.63 Å. In the second Fe site, Fe is bonded in a 12-coordinate geometry to two Y, seven Fe, and two equivalent Al atoms. There are a spread of Fe–Fe bond distances ranging from 2.49–2.55 Å. Both Fe–Al bond lengths are 2.49 Å. In the third Fe site, Fe is bonded in a 12-coordinate geometry to three Y, seven Fe, and two equivalent Al atoms. Both Fe–Fe bond lengths are 2.47 Å. Both Fe–Al bond lengths are 2.47 Å. Al is bonded to two equivalent Y and ten Fe atoms to form a mixture of distorted face and corner-sharing AlY2Fe10 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2AlFe3 by Materials Project

Y2Fe3Al is Cubic Laves-derived structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to four equivalent Y, nine equivalent Fe, and three equivalent Al atoms. There are one shorter (3.13 Å) and three longer (3.23 Å) Y–Y bond lengths. There are six shorter (3.05 Å) and three longer (3.10 Å) Y–Fe bond lengths. All Y–Al bond lengths are 3.07 Å. Fe is bonded to six equivalent Y, four equivalent Fe, and two equivalent Al atoms to form FeY6Al2Fe4 cuboctahedra that share corners with four equivalent AlY6Fe6 cuboctahedra, corners with fourteen equivalent FeY6Al2Fe4 cuboctahedra, edges with six equivalent FeY6Al2Fe4 cuboctahedra, faces with six equivalent AlY6Fe6 cuboctahedra, and faces with twelve equivalent FeY6Al2Fe4 cuboctahedra. All Fe–Fe bond lengths are 2.61 Å. Both Fe–Al bond lengths are 2.61 Å. Al is bonded to six equivalent Y and six equivalent Fe atoms to form AlY6Fe6 cuboctahedra that share corners with six equivalent AlY6Fe6 cuboctahedra, corners with twelve equivalent FeY6Al2Fe4 cuboctahedra, edges with six equivalent AlY6Fe6 cuboctahedra, and faces with eighteen equivalent FeY6Al2Fe4 cuboctahedra.

36 MATERIALS SCIENCE↗