Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “CrNi”

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.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Metastable formation and disordering kinetics of body-centered orthorhombic CrNi 2 laths in a Cr-Ni binary alloy

Chromium (Cr) alloys combine low density with high-temperature strength but suffer from brittleness and rapid softening. Body-centered orthorhombic (BCO) CrNi 2 laths have been shown to improve Cr-alloy high-temperature strength retention, yet their thermal stability and transformation behavior remain unclear. CrNi 2 conventionally forms through long-range ordering from a face-centered cubic (FCC) phase. Using multiscale microscopy and neutron diffraction, we show that CrNi 2 instead nucleates from a body-centered cubic (BCC) matrix, in a binary Cr 85 Ni 15 alloy. Despite aging above the equilibrium ordering temperature, CrNi 2 persists for ∼220 h at 760 °C before fully disordering, indicating sluggish transformation kinetics. The formation and decomposition follow differing transformation pathways (BCC → CrNi 2 → FCC), revealing kinetic asymmetry not captured by equilibrium Cr-Ni phase diagrams. In conclusion, these findings redefine the transformation behavior of CrNi 2 , establish its metastable kinetic window, and suggest alloying strategies to stabilize CrNi 2 for precipitation strengthening of high-temperature Cr-alloys.

CrNi2 transformation kinetics↗
DOE OSTI2020

Materials Data on CrNi(PO4)2 by Materials Project

CrNi(PO4)2 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. Cr4+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent NiO6 octahedra, corners with four PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–51°. There are a spread of Cr–O bond distances ranging from 1.95–2.03 Å. Ni2+ is bonded to six O2- atoms to form distorted NiO6 octahedra that share corners with four equivalent CrO6 octahedra, corners with four PO4 tetrahedra, and an edgeedge with one PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–51°. There are a spread of Ni–O bond distances ranging from 1.96–2.32 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one NiO6 octahedra, corners with three equivalent CrO6 octahedra, and an edgeedge with one NiO6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of P–O bond distances ranging from 1.52–1.58 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one CrO6 octahedra, corners with three equivalent NiO6 octahedra, and an edgeedge with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 41–59°. There are a spread of P–O bond distances ranging from 1.51–1.59 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cr4+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 120 degrees geometry to one Ni2+ and one P5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Cr4+, one Ni2+, and one P5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Cr4+, one Ni2+, and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cr4+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ni2+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrNi by Materials Project

NiCr is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cr is bonded in a body-centered cubic geometry to eight equivalent Ni atoms. All Cr–Ni bond lengths are 2.51 Å. Ni is bonded in a body-centered cubic geometry to eight equivalent Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrNi(PO4)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 OSTI2025

Microstructural features underpinning the mechanical behavior of powder metallurgy Cr-based alloys

Refractory materials such as Cr-based alloys offer the potential of enhanced elevated temperature performance but have been limited by their poor formability. However, powder metallurgy has been shown to be a viable pathway to fabricate these alloys. Nanophase separation sintering (NPSS) in particular has been used in the literature to accelerate the densification of powder metallurgy Cr- and W-based alloys. Here, we explore microstructure evolution during NPSS in a binary Cr 85 Ni 15 alloy consolidated via (i) cold pressing & pressureless sintering and (ii) hot isostatic pressing followed by hot extrusion & hot upsetting, and the role of these different processing routes on resulting material properties. The alloy lacked room temperature tensile ductility regardless of consolidation process, with multi-length scale characterization, including scanning electron microscopy, transmission electron microscopy, atom probe tomography, X-ray diffraction, and uniaxial tensile testing, revealing that brittleness was due to intrinsically poor Cr grain boundary cohesion. Tensile testing conducted at 760 °C showed marked strength reduction for the extruded & upset (94 %) condition compared to the pressed & sintered (18 %). The formation of orthorhombic CrNi 2 intermetallics functioned as precipitate strengtheners and prevented elevated temperature softening in the pressed and sintered condition. The findings offer foundational insights into aiding the future development of Cr-based alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Theoretical antiferromagnetism of ordered face-centered cubic Cr-Ni alloys

Contrary to prior calculations, the Ni-rich ordered structures of the Cr-Ni alloy system are found to be antiferromagnetic under semilocal density-functional theory. The optimization of local magnetic moments significantly increases the driving force for the formation of CrNi 2 , the only experimentally observed intermetallic phase. This structure's ab initio magnetism appears well described by a Heisenberg Hamiltonian with longitudinal spin fluctuations; itinerant Cr moments are induced only by the strength of exchange interactions. The role of magnetism at temperature is less clear and several scenarios are considered based on a review of experimental literature, specifically a failure of the theory, the existence of an overlooked magnetic phase transition, and the coupling of antiferromagnetism to chemical ordering. In conclusion, implications for related commercial and high-entropy alloys are discussed for each case.

36 MATERIALS SCIENCE↗
NASA NTRS2007

Molecules and Dust in the Humunculus: Ejecta of Eta Carinae

In the 18401s, Eta Carinae ejected massive amounts of nitrogen-rich, carbon- and oxygen-poor material which we see as the hourglass-shaped Homunculus. With the Hubble Space Telescope Imaging Spectrograph, we detected multiple shells in line of sight, the most massive and intriguing being at -513 km/s. Numerous lines of Fe I, Fe II, Ni II, Cr II, Sc II, Sr II, Ti II, V II, etc are identified as well as nearly a thousand H2 lines. The metals have energy level populations consistent with 760K and excited by photons < 8.5eV. We have now identified CH, CH+, OH, and NH at the same velocity, but at 60K, suggesting stratification in the outer ejecta. Analysis of the interior, photoionized emission hourglass structure, known as the Little Homunculus, indicates He, N overabundances and C, 0 underabundances (approximately 1/80 solar). A skirt of neutral and partially ionized gas lies between the lobes of the hourglasses. A portion is seen as the Strontium Filament, a metal- ionized, neutral hydrogen structure. Relative abundances of TiNi are 1/80 solar, CrNi are 1/20 solar. This complex of ejecta appears to have been ejected by a massive star(s) at the end of the hydrogen-burning phase when convection led to overproduction of nitrogen at the expense of carbon and oxygen. Given the underabundances of carbon and oxygen, the chemistry of this system is quite different to the normal ISM, leading to a nitrogen- dominated chemistry. What little C and 0 that is formed is immediately taken up by SiO and Al0 molecules leading to a very different gas/dust ratio than the normal ISM. Dust in this ejecta is abundance, but known to be very grey in character. Observations with HST/STIS and VLT/UVES will be presented along with simple physical models and CLOUD modeling. Insight by the participants will be solicited.

Gull, T.↗