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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.

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13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

A TEM quantitative evaluation of strengthening in an Mg-RE alloy reinforced with SiC

Magnesium alloys containing rare earth elements are known to have high specific strength, good creep and corrosion resistance up to 523 K. The addition of SiC ceramic particles strengthens the metal matrix composite resulting in better wear and creep resistance while maintaining good machinability. The role of the reinforcement particles in enhancing strength can be quantitatively evaluated using transmission electron microscopy (TEM). This paper presents a quantitative evaluation of the different strengthening contributions, determined through TEM inspections, in an SiC Mg-RE composite alloy containing yttrium, neodymium, gadolinium and dysprosium. Compression tests at temperatures ranging between 290 and 573 K were carried out. The microstructure strengthening mechanism was studied for all the compression conditions. Strengthening was compared to the mechanical results and the way the different contributions were combined is also discussed and justified. - Research Highlights: {yields} TEM yield strengthening terms evaluation on a Mg-RE SiC alloy. {yields} The evaluation has been extended to different compression temperature conditions. {yields} Linear and Quadratic sum has been proposed and validated. {yields} Hall-Petch was found to be the most prominent strengthening contributions.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A unified description of ordering in HCP Mg-RE alloys

High throughput first-principles calculations were employed to unravel the thermodynamic stability of two sets of hierarchical phases, β P ''' and β S ''' , in Mg-RE (rare-earth) alloys. The β P ''' orderings (with compositions greater than x RE =0.125) are predicted to form in the Mg-{La,Ce,Pr,Nd,Pm,Sm} binary alloys, thus explaining experimental observations of RE atoms arranged as hexagonal rings in these alloys. Mg-{Sc,Y,Tb,Dy,Ho,Er,Tm,Lu} alloys are predicted to form β S ' (x RE =0.125) precipitates without hexagonal ring arrangements. The calculated misfit strains are used to infer the qualitative shapes of the precipitates and their relative aspect ratios. High aspect-ratio precipitates may be formed using alloying elements that encourage the formation of β P ''' . The predictions in this study can be used to inform alloy design of precipitation strengthened magnesium alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Analysis of the Deformation Behavior of Mg-RE and Mg-Li Alloys using In-situ Energy-dispersive Synchrotron X-ray Diffraction

EPSC-Model is able to predict the complex deformation behavior of Mg-RE and Mg-Li alloys within a wide range of strains. Modification of the texture by RE-elements and the addition of Li increases the activity of slip systems at low strains - Reorientation due to twinning is stretch over a larger range of plastic deformation. Deformation at high strains is realized mainly by the basal and the <c+a>-pyramidal slip systems.

36 MATERIALS SCIENCE↗
DOE OSTI2016

In-situ analysis of the slip activity during tensile deformation of cast and extruded Mg-10Gd-3Y-0.5Zr (wt.%) at 250 °C

The slip activity and slip interaction in tensile deformation of peak-aged cast and extruded Mg-10Gd-3Y-0.5Zr (wt.%) at 250 °C was investigated using in-situ scanning electron microscopy. Basal slip was the most likely system to be activated during the tensile deformation, while prismatic < a > and pyramidal < c + a > slip also contributed to the deformation. No twinning was observed. The number of non-basal slip systems accounted for ~ 36% of the total active slip systems for the cast alloy, while non-basal slip accounted for 12–17% of the total deformation observations in the extruded alloy. Multiple-slip was observed within grains, and the basal/prismatic pairing type dominated the multiple-slip observations. Slip transfer occurred across grain boundaries and most of the slip transfer observations showed basal-basal type. The involved slip systems of slip transfer pairs were always associated with the same < a > direction. The slip transfer occurred more easily at low angle boundaries (LABs) and boundaries with misorientations greater than 75°. - Highlights: • Slip deformation of a Mg-RE alloy at 250 °C was investigated using in-situ SEM. • The extruded-T5 GW103 alloy did not exhibit a high anisotropic behavior. • Multiple-slip was observed within grains, and basal/prismatic type dominated. • Slip transfer occurred and most of the observations showed basal-basal type. • Slip transfer occurred more easily at LABs and boundaries with misorientations > 75°.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Experimental characterization and atomistic simulation of grain boundary segregation in Mg-Y alloys

As a rare earth solute element in Mg alloys, Y has the beneficial effects of increasing both the strength and the ductility as well as weakening the crystallographic texture. To achieve a more fundamental understanding on how Y addition affects the microstructural evolution and mechanical properties, the Y segregation behavior at grain boundaries was investigated in Mg-1wt.%Y and Mg-7wt.%Y alloys at different conditions. The segregation intensity and its dependence on the grain boundary misorientation angle were experimentally characterized and computationally predicted. Strong segregation at grain boundaries was observed in both low and high Y-containing alloys. Y segregation was found to remain in alloy Mg-7Y after high-temperature annealing heat treatment at 540 °C. No direct correlation between the Y segregation intensity and the grain boundary misorientation angle could be established based on either the experimental characterization or the atomistic simulation with a spectral model. We thus conclude that grain boundary segregation of Y is independent of grain boundary misorientation angle.

Grain boundary↗
DOE OSTI2022

Partitioning of Ca to metastable precipitates in a Mg-rare earth alloy

The potential effect of the element Ca on the precipitation behavior was investigated in an Mg-rare earth alloy. A combination of metastable β''' and β' precipitates was observed for the peak aging condition at 200°C. Ca addition was found to have no significant effect on the precipitating phases and evolution sequence. Composition analysis showed that the Ca partitioned to both β''' and β' precipitate phases. First-principles calculations indicated that Ca partitions to the rare-earth sublattice in the precipitate phase. This finding suggests the potential of Ca to partially replace costly rare-earth elements in precipitation-hardened Mg-rare earth alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Re by Materials Project

Mg3Re is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Mg is bonded to eight equivalent Mg and four equivalent Re atoms to form distorted MgMg8Re4 cuboctahedra that share corners with twelve equivalent MgMg8Re4 cuboctahedra, edges with eight equivalent ReMg12 cuboctahedra, edges with sixteen equivalent MgMg8Re4 cuboctahedra, faces with four equivalent ReMg12 cuboctahedra, and faces with fourteen equivalent MgMg8Re4 cuboctahedra. All Mg–Mg bond lengths are 2.94 Å. All Mg–Re bond lengths are 2.94 Å. Re is bonded to twelve equivalent Mg atoms to form ReMg12 cuboctahedra that share corners with twelve equivalent ReMg12 cuboctahedra, edges with twenty-four equivalent MgMg8Re4 cuboctahedra, faces with six equivalent ReMg12 cuboctahedra, and faces with twelve equivalent MgMg8Re4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgRe3 by Materials Project

MgRe3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mg is bonded in a distorted body-centered cubic geometry to fourteen Re atoms. There are eight shorter (2.70 Å) and six longer (3.11 Å) Mg–Re bond lengths. There are two inequivalent Re sites. In the first Re site, Re is bonded to four equivalent Mg and four equivalent Re atoms to form a mixture of distorted edge, face, and corner-sharing ReMg4Re4 tetrahedra. All Re–Re bond lengths are 2.70 Å. In the second Re site, Re is bonded in a 8-coordinate geometry to six equivalent Mg and eight equivalent Re atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Materials Data on Mg149Re by Materials Project

Mg149Re is alpha Samarium-derived structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. there are twenty-seven inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share a cornercorner with one ReMg12 cuboctahedra, corners with sixteen MgMg12 cuboctahedra, edges with fourteen MgMg12 cuboctahedra, and faces with nineteen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.16–3.33 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to eleven Mg and one Re atom. There are a spread of Mg–Mg bond distances ranging from 2.96–3.27 Å. The Mg–Re bond length is 3.00 Å. In the third Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with sixteen MgMg12 cuboctahedra, an edgeedge with one ReMg12 cuboctahedra, edges with thirteen MgMg12 cuboctahedra, and faces with eighteen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.16–3.21 Å. In the fourth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are four shorter (3.19 Å) and four longer (3.20 Å) Mg–Mg bond lengths. In the fifth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with sixteen MgMg12 cuboctahedra, an edgeedge with one ReMg12 cuboctahedra, edges with seventeen MgMg12 cuboctahedra, and faces with sixteen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.17–3.23 Å. In the sixth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.20 Å. In the seventh Mg site, Mg is bonded in a distorted single-bond geometry to nine Mg and one Re atom. There are a spread of Mg–Mg bond distances ranging from 3.23–3.32 Å. The Mg–Re bond length is 3.00 Å. In the eighth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with sixteen MgMg12 cuboctahedra, an edgeedge with one ReMg12 cuboctahedra, edges with fifteen MgMg12 cuboctahedra, and faces with seventeen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.17–3.22 Å. In the ninth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are four shorter (3.19 Å) and three longer (3.20 Å) Mg–Mg bond lengths. In the tenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are one shorter (3.19 Å) and four longer (3.20 Å) Mg–Mg bond lengths. In the eleventh Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.16–3.20 Å. In the twelfth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.20 Å. In the thirteenth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with sixteen MgMg12 cuboctahedra, edges with fifteen MgMg12 cuboctahedra, a faceface with one ReMg12 cuboctahedra, and faces with fifteen MgMg12 cuboctahedra. There are two shorter (3.17 Å) and one longer (3.18 Å) Mg–Mg bond lengths. In the fourteenth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share a cornercorner with one ReMg12 cuboctahedra, corners with fifteen MgMg12 cuboctahedra, edges with seventeen MgMg12 cuboctahedra, and faces with seventeen MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.16–3.23 Å. In the fifteenth Mg site, Mg is bonded to twelve Mg atoms to form MgMg12 cuboctahedra that share corners with twelve MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, a faceface with one ReMg12 cuboctahedra, and faces with sixteen MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.20 Å. In the sixteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.18–3.21 Å. In the seventeenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are three shorter (3.19 Å) and two longer (3.20 Å) Mg–Mg bond lengths. In the eighteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are two shorter (3.19 Å) and three longer (3.20 Å) Mg–Mg bond lengths. In the nineteenth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are five shorter (3.19 Å) and two longer (3.20 Å) Mg–Mg bond lengths. In the twentieth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.19 Å. In the twenty-first Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are four shorter (3.18 Å) and two longer (3.20 Å) Mg–Mg bond lengths. In the twenty-second Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.18 Å. In the twenty-third Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are one shorter (3.18 Å) and four longer (3.19 Å) Mg–Mg bond lengths. In the twenty-fourth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are two shorter (3.19 Å) and one longer (3.20 Å) Mg–Mg bond lengths. In the twenty-fifth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. In the twenty-sixth Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.20 Å. In the twenty-seventh Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. Re is bonded to twelve Mg atoms to form ReMg12 cuboctahedra that share corners with eighteen MgMg12 cuboctahedra, edges with eighteen MgMg12 cuboctahedra, and faces with eight MgMg12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg3Re by Materials Project

Mg3Re is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Mg is bonded to eight equivalent Mg and four equivalent Re atoms to form distorted MgMg8Re4 cuboctahedra that share corners with four equivalent ReMg12 cuboctahedra, corners with fourteen equivalent MgMg8Re4 cuboctahedra, edges with six equivalent ReMg12 cuboctahedra, edges with twelve equivalent MgMg8Re4 cuboctahedra, faces with four equivalent ReMg12 cuboctahedra, and faces with sixteen equivalent MgMg8Re4 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 2.81–3.10 Å. There are two shorter (2.90 Å) and two longer (2.96 Å) Mg–Re bond lengths. Re is bonded to twelve equivalent Mg atoms to form ReMg12 cuboctahedra that share corners with six equivalent ReMg12 cuboctahedra, corners with twelve equivalent MgMg8Re4 cuboctahedra, edges with eighteen equivalent MgMg8Re4 cuboctahedra, faces with eight equivalent ReMg12 cuboctahedra, and faces with twelve equivalent MgMg8Re4 cuboctahedra.

36 MATERIALS SCIENCE↗