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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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10 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Solutionization via Severe Plastic Deformation: Effect on Natural Aging in an Al-Mg-Si-(Mn) Alloy

Shear Assisted Processing and Extrusion (ShAPE), a severe plastic deformation technique that is fast and scalable, was used to produce thin-wall tubing from alloy 6082 (Al-0.8Mg-0.9Si-0.7Mn) with in-situ solutionization during processing quickly followed by quenching. Quench medium and input material heat treatment were varied and natural aging behavior (T1 heat treatment) was evaluated using tensile testing. As-cast input material was found to have higher strength early in post-ShAPE natural aging and homogenized input material was found to have strengthening during natural aging. Compared to air quenching, water quenching gave greater strength both early in and after natural aging. These observations along with microscopy suggest that: 1. air quenching was too slow; 2. as-cast material was not fully solutionized but plastic deformation broke up the coarse intermetallic particles, which provided strengthening; and 3. homogenized material was solutionized well, which led to good natural aging behavior.

Milligan, Brian K.↗
DOE OSTI2020

Thermodynamic Modeling of the Al-Ce-Cu-Mg-Si System and Its Application to Aluminum-Cerium Alloy Design

Recently discovered AlCe alloys have shown promise in a number of applications, but the propensity of Ce to react with Al and other alloying elements can complicate the phase equilibria and design approach. To solve this, the CALPHAD method is used to explore an alloy within the quinary Al-Ce-Cu-Mg-Si system by developing a thermodynamic database with self-consistent parameters. The database includes a description of all 10 binary systems and 8 ternary systems consisting of: (i) 6 Al-containing ternaries (Al-Ce-Cu, Al-Ce-Mg, Al-Ce-Si, Al-Cu-Mg, Al-Cu-Si and Al-Mg-Si); and (ii) 2 additional ternaries that include Mg and Si (i.e., Ce-Mg-Si and Cu-Mg-Si). The thermodynamic description for the Al-Ce-Mg and Al-Mg-Si systems were reassessed to ensure consistency with the binary systems and the Ce-Mg-Si system is presented for the first time and compared to theoretical data from DFT (Density Functional Theory). In addition to the ternary interactions, the quaternary compound Al3Cu2Mg9Si7 and solid solution extending from the ternary Al2CuMg phase (Al,Si)2CuMg are incorporated. The CALPHAD method is employed and leveraged through the use of a Materials Design Simulator (MDS) to accelerate the design of novel aluminum-cerium-based alloys. The combination of a CALPHAD-based framework with experimental efforts and industrial insight permits the development of three new Al-Ce alloys: Al-3.5Ce-0.4Mg-7Si (Ce-modified A356), Al-5Ce-1Cu-0.5Mg-10Si and Al-19Ce-0.9Mg-1.1Si.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Impact of droplet oxidation on mechanical properties of an Al-7Si-0.4Mg alloy fabricated with liquid metal jetting

Droplet-on-demand liquid metal jetting (DOD-LMJ) is a new method for additive manufacturing of bulk structural alloys. Here, we report on the microstructure, tensile, and fatigue properties of an Al-7Si-0.4Mg (A356) alloy fabricated with LMJ. Liquid metal droplets were shielded by high-purity Ar gas shroud during deposition. Atom probe tomography revealed that a few nanometers thick (Al-Mg-Si)-O oxide film formed on the droplets despite Ar gas shielding. Tensile tests on peak-aged LMJ A356 alloy showed that yield strength was isotropic (250 MPa), but ductility was lower in the build direction (6.1 ± 1.4 %) compared to the transverse direction (9.4 ± 1.0 %). Lower ductility in the build direction was attributed to delamination of metal-oxide interfaces at layer boundaries. The ductility and yield strength of LMJ A356 were similar to cast A356 and laser powder bed fused (LPBF) A357 alloys, indicating the limited impact of oxide film on tensile properties. The oxide film severely impacted the fatigue properties. Fatigue resistance of LMJ A356 was limited by fatigue crack initiation at lack-of-fusion defects and fatigue crack propagation along layer boundaries by delamination of the metal-oxide interface. The fatigue strength of LMJ A356 at 60 MPa was lower than cast A356 and LPBF A357 alloys in the peak-aged condition. This research underscores the need for managing droplet oxidation during LMJ additive manufacturing of structural alloys.

42 ENGINEERING↗
NASA NTRS1988

Low cycle fatigue

The papers contained in this volume focus on various aspects of low cycle fatigue, including cyclic deformation, crack propagation, high-temperature low cycle fatigue, microstructural defects, multiaxial and variable amplitude loading, and life prediction. Papers are presented on the low cycle fatigue of some aluminum alloys, prediction of crack growth under creep-fatigue loading conditions, high-temperature low cycle fatigue behavior and lifetime prediction of a nickel-base ODS alloy, and an integrated approach to creep-fatigue life prediction. Other topics discussed include thermal fatigue testing of coated monocrystalline superalloys, low cycle fatigue of Al-Mg-Si alloys, and the effect of superimposed stresses at high frequency on low cycle fatigue.

Solomon, H. D.↗
DOE OSTI2020

Materials Data on Mg4AlSi6 by Materials Project

Mg4AlSi6 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 9-coordinate geometry to two Mg, one Al, and eight Si atoms. There are one shorter (2.95 Å) and one longer (3.19 Å) Mg–Mg bond lengths. The Mg–Al bond length is 2.99 Å. There are a spread of Mg–Si bond distances ranging from 2.95–3.04 Å. In the second Mg site, Mg is bonded in a 8-coordinate geometry to one Mg, one Al, and seven Si atoms. The Mg–Al bond length is 2.74 Å. There are a spread of Mg–Si bond distances ranging from 2.77–3.04 Å. Al is bonded in a 8-coordinate geometry to four Mg and four equivalent Si atoms. All Al–Si bond lengths are 2.62 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to six Mg, two equivalent Al, and one Si atom. The Si–Si bond length is 2.40 Å. In the second Si site, Si is bonded in a 8-coordinate geometry to five Mg and three equivalent Si atoms. There are two shorter (2.45 Å) and one longer (2.50 Å) Si–Si bond lengths. In the third Si site, Si is bonded in a 8-coordinate geometry to four Mg and four Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(AlSi)2 by Materials Project

MgAl2Si2 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. Mg2+ is bonded to six equivalent Si4- atoms to form MgSi6 octahedra that share corners with twelve equivalent AlSi4 tetrahedra, edges with six equivalent MgSi6 octahedra, and edges with six equivalent AlSi4 tetrahedra. All Mg–Si bond lengths are 2.86 Å. Al3+ is bonded to four equivalent Si4- atoms to form AlSi4 tetrahedra that share corners with six equivalent MgSi6 octahedra, corners with six equivalent AlSi4 tetrahedra, edges with three equivalent MgSi6 octahedra, and edges with three equivalent AlSi4 tetrahedra. The corner-sharing octahedra tilt angles range from 16–55°. There are three shorter (2.49 Å) and one longer (2.61 Å) Al–Si bond lengths. Si4- is bonded to three equivalent Mg2+ and four equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing SiMg3Al4 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAlSi by Materials Project

AlMgSi crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg is bonded in a 5-coordinate geometry to four equivalent Al and five equivalent Si atoms. There are two shorter (3.04 Å) and two longer (3.12 Å) Mg–Al bond lengths. There are a spread of Mg–Si bond distances ranging from 2.81–2.93 Å. Al is bonded in a 4-coordinate geometry to four equivalent Mg and four equivalent Si atoms. There are a spread of Al–Si bond distances ranging from 2.57–2.63 Å. Si is bonded in a 9-coordinate geometry to five equivalent Mg and four equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg2(AlSi2)3 by Materials Project

Mg2(AlSi2)3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Mg is bonded in a 12-coordinate geometry to two equivalent Mg, two Al, and eight Si atoms. Both Mg–Mg bond lengths are 2.98 Å. There are one shorter (2.73 Å) and one longer (3.09 Å) Mg–Al bond lengths. There are a spread of Mg–Si bond distances ranging from 2.77–2.95 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 11-coordinate geometry to one Mg, two Al, and eight Si atoms. There are one shorter (2.90 Å) and one longer (2.91 Å) Al–Al bond lengths. There are a spread of Al–Si bond distances ranging from 2.68–2.84 Å. In the second Al site, Al is bonded in a 6-coordinate geometry to two equivalent Mg, two equivalent Al, and four equivalent Si atoms. All Al–Si bond lengths are 2.82 Å. There are three inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to three equivalent Mg, two equivalent Al, and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.49–2.70 Å. In the second Si site, Si is bonded in a 10-coordinate geometry to two equivalent Mg, six Al, and two Si atoms. The Si–Si bond length is 2.73 Å. In the third Si site, Si is bonded in a 8-coordinate geometry to three equivalent Mg, two equivalent Al, and three equivalent Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg4AlSi3 by Materials Project

Mg4AlSi3 crystallizes in the tetragonal P4/ncc space group. The structure is three-dimensional. Mg is bonded in a 5-coordinate geometry to one Al and five Si atoms. The Mg–Al bond length is 3.06 Å. There are a spread of Mg–Si bond distances ranging from 2.79–2.97 Å. Al is bonded in a 5-coordinate geometry to four equivalent Mg and five Si atoms. There are four shorter (2.60 Å) and one longer (2.80 Å) Al–Si bond lengths. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to eight equivalent Mg and one Al atom. In the second Si site, Si is bonded in a 9-coordinate geometry to six equivalent Mg, two equivalent Al, and one Si atom. The Si–Si bond length is 2.46 Å.

36 MATERIALS SCIENCE↗