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At least 19 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 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 NTRS1947

Elastic Properties in Tension and Shear of High Strength Nonferrous Metals and Stainless Steel - Effect of Previous Deformation and Heat Treatment

A resume is given of an investigation of the influence of plastic deformation and of annealing temperature on the tensile and shear elastic properties of high strength nonferrous metals and stainless steels in the form of rods and tubes. The data were obtained from earlier technical reports and notes, and from unpublished work in this investigation. There are also included data obtained from published and unpublished work performed on an independent investigation. The rod materials, namely, nickel, monel, inconel, copper, 13:2 Cr-Ni steel, and 18:8 Cr-Ni steel, were tested in tension; 18:8 Cr-Ni steel tubes were tested in shear, and nickel, monel, aluminum-monel, and Inconel tubes were tested in both tension and shear. There are first described experiments on the relationship between hysteresis and creep, as obtained with repeated cyclic stressing of annealed stainless steel specimens over a constant load range. These tests, which preceded the measurements of elastic properties, assisted in devising the loading time schedule used in such measurements. From corrected stress-set curves are derived the five proof stresses used as indices of elastic or yield strength. From corrected stress-strain curves are derived the secant modulus and its variation with stress. The relationship between the forms of the stress-set and stress-strain curves and the values of the properties derived is discussed. Curves of variation of proof stress and modulus with prior extension, as obtained with single rod specimens, consist in wavelike basic curves with superposed oscillations due to differences of rest interval and extension spacing; the effects of these differences are studied. Oscillations of proof stress and modulus are generally opposite in manner. The use of a series of tubular specimens corresponding to different amounts of prior extension of cold reduction gave curves almost devoid of oscillation since the effects of variation of rest interval and extension spacing were removed. Comparison is also obtained between the variation of the several properties, as measured in tension and in shear. The rise of proof stress with extension is studied, and the work-hardening rates of the various metals evaluated. The ratio between the tensile and shear proof stresses for the various annealed and cold-worked tubular metals is likewise calculated. The influence of annealing or tempering temperature on the proof stresses and moduli for the cold-worked metals and for air-hardened 13:2 Cr-Ni steel is investigated. An improvement of elastic strength generally is obtained, without important loss of yield strength, by annealing at suitable temperature. The variation of the proof stress and modulus of elasticity with plastic deformation or annealing temperature is explained in terms of the relative dominance of three important factors: namely, (a) internal stress, (b) lattice-expansion or work-hardening, and (c) crystal reorientation. Effective values of Poisson's ratio were computed from tensile and shear moduli obtained on tubular specimens. The variation of Poisson's ratio with plastic deformation and annealing temperature is explained in terms of the degree of anisotropy produced by changes of (a) internal stress and (b) crystal orientation.

METALS - ELASTICITY↗
NASA NTRS1999

Massive Chromite in the Brenham Pallasite and the Fractionation of Cr During the Crystallization of Asteroidal Cores

Large (greater than or equal to 2 mm) chromite grains are present in IIIAB iron meteorites and in the main-group a pallasites (PMG), closely related to high-Au IIIAB irons, Pallasites seem to have formed by the intrusion of a highly evolved metallic magma from a IIIAB-like core into fragmented olivine of the overlying dunite mantle. High Cr contents are commonly encountered during the analyses of metallic samples of high-Au IIIAB irons and main-group pallasites, an indication that Cr contents were high in the intruding liquid and that Cr behaved as an incompatible element during the crystallization of the IIIAB magma, contrary to expectations based on the negative IIIAB Cr-Ni and Cr-Au trends among low-Au IIIAB irons. In a region about 10 cm across in the Brenham main-group pallasite massive chromite fills the interstices between olivine grains, the site normally occupied by metal in Brenham and other pallasites. The massive chromite may have formed as a late cumulus phase; because Fe-Ni was also crystallizing, its absence in the chromite-rich region suggests a separation associated with differences in liquid buoyancy. The coexisting chromite and olivine are zoned; in the olivine FeO is highest in pallasitic (olivine-metal) regions, lowest in rims adjacent to chromite, and intermediate in the cores of these olivines. Chromite shows the opposite zoning, with the highest FeO contents at grain edges adjacent to olivine. The observed gradients are those expected to form by Fe-Mg exchange between olivine and chromite during slow cooling at subsolidus temperatures. Compared to normal Brenham, contents of phosphoran olivine and phosphates are higher in the chromitic pallasitic region. We also report data for large-to-massive chromites present in PMG Molong and in high-Au IIIAB Bear Creek that, like Brenham, formed from a highly evolved magma. The Bear Creek chromite has a much lower Mg content than that in the pallasites, implying that, in the PMG, the Mg was extracted from the olivine during high-temperature reaction with the precipitating chromite. There are other circumstantial arguments indicating that Cr was incompatible in the metal during the crystallization of the IIIAB magma, with the concentration in die residual magma rising from an initial value of about 300 micrograms/g to a value around 700 micrograms/g when Bear Creek and Brenham were formed. We consider possible explanations for these negative Cr-Au and Cr-Ni trends and find the most probable one to be that they reflect sampling artefacts resulting from analysts avoiding visible chromite (and the commonly associated phase FeS) when choosing metal samples.

Wasson, John T.↗
DOE OSTI2025

Analytical gradient-based optimization of CALPHAD model parameters

The calibration of CALPHAD (CALculation of PHAse Diagrams) models involves the solution of a very challenging high-dimensional multiobjective optimization problem. Traditional approaches to parameter fitting predominantly rely on gradient-free methods, which while robust, are computationally inefficient and often scale poorly with model complexity. In this work, we introduce and demonstrate a generalizable framework for analytic gradient-based optimization of the parameters of the CALPHAD model enabled by the recently formalized Jansson derivative technique. This method allows for efficient evaluation of gradients of thermodynamic properties at equilibrium with respect to model parameters, even in the presence of arbitrarily complex internal degrees of freedom. Leveraging these semi-analytic gradients, we employ the conjugate gradient (CG) method to optimize thermodynamic model parameters for four binary alloy systems: Cu-Mg, Fe-Ni, Cr-Ni, and Cr-Fe. Across all systems, CG achieves comparable or superior optimality relative to Bayesian ensemble Markov Chain Monte Carlo (MCMC) with improvements in computational efficiency ranging from one to three orders of magnitude. Furthermore, our results establish a new paradigm for CALPHAD assessments in which high fidelity data-rich model calibration becomes tractable using deterministic gradient-informed algorithms.

CALPHAD↗
DOE OSTI2020

Materials Data on CrNi2 by Materials Project

Ni2Cr crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Cr is bonded to two equivalent Cr and ten equivalent Ni atoms to form CrCr2Ni10 cuboctahedra that share corners with two equivalent CrCr2Ni10 cuboctahedra, corners with ten equivalent NiCr5Ni7 cuboctahedra, edges with twelve equivalent CrCr2Ni10 cuboctahedra, edges with twelve equivalent NiCr5Ni7 cuboctahedra, faces with four equivalent CrCr2Ni10 cuboctahedra, and faces with fourteen equivalent NiCr5Ni7 cuboctahedra. Both Cr–Cr bond lengths are 2.47 Å. There are two shorter (2.48 Å) and eight longer (2.49 Å) Cr–Ni bond lengths. Ni is bonded to five equivalent Cr and seven equivalent Ni atoms to form NiCr5Ni7 cuboctahedra that share corners with five equivalent CrCr2Ni10 cuboctahedra, corners with seven equivalent NiCr5Ni7 cuboctahedra, edges with six equivalent CrCr2Ni10 cuboctahedra, edges with eighteen equivalent NiCr5Ni7 cuboctahedra, faces with seven equivalent CrCr2Ni10 cuboctahedra, and faces with eleven equivalent NiCr5Ni7 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.46–2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrNi3 by Materials Project

Ni3Cr is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Cr is bonded to twelve Ni atoms to form CrNi12 cuboctahedra that share corners with four equivalent CrNi12 cuboctahedra, corners with eight equivalent NiCr4Ni8 cuboctahedra, edges with eight equivalent CrNi12 cuboctahedra, edges with sixteen equivalent NiCr4Ni8 cuboctahedra, faces with four equivalent CrNi12 cuboctahedra, and faces with fourteen NiCr4Ni8 cuboctahedra. There are four shorter (2.48 Å) and eight longer (2.50 Å) Cr–Ni bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Cr and eight equivalent Ni atoms to form NiCr4Ni8 cuboctahedra that share corners with four equivalent NiCr4Ni8 cuboctahedra, corners with eight equivalent CrNi12 cuboctahedra, edges with twenty-four NiCr4Ni8 cuboctahedra, faces with six equivalent CrNi12 cuboctahedra, and faces with twelve NiCr4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.50 Å. In the second Ni site, Ni is bonded to four equivalent Cr and eight Ni atoms to form NiCr4Ni8 cuboctahedra that share corners with twelve equivalent NiCr4Ni8 cuboctahedra, edges with eight equivalent CrNi12 cuboctahedra, edges with sixteen NiCr4Ni8 cuboctahedra, faces with four equivalent CrNi12 cuboctahedra, and faces with fourteen NiCr4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.48 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrNi3 by Materials Project

Ni3Cr is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cr is bonded to twelve equivalent Ni atoms to form CrNi12 cuboctahedra that share corners with twelve equivalent CrNi12 cuboctahedra, edges with twenty-four equivalent NiCr4Ni8 cuboctahedra, faces with six equivalent CrNi12 cuboctahedra, and faces with twelve equivalent NiCr4Ni8 cuboctahedra. All Cr–Ni bond lengths are 2.51 Å. Ni is bonded to four equivalent Cr and eight equivalent Ni atoms to form NiCr4Ni8 cuboctahedra that share corners with twelve equivalent NiCr4Ni8 cuboctahedra, edges with eight equivalent CrNi12 cuboctahedra, edges with sixteen equivalent NiCr4Ni8 cuboctahedra, faces with four equivalent CrNi12 cuboctahedra, and faces with fourteen equivalent NiCr4Ni8 cuboctahedra. All Ni–Ni bond lengths are 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrNi3 by Materials Project

Ni3Cr is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cr is bonded in a distorted body-centered cubic geometry to fourteen Ni atoms. There are eight shorter (2.44 Å) and six longer (2.82 Å) Cr–Ni bond lengths. There are two inequivalent Ni sites. In the first Ni site, Ni is bonded in a distorted body-centered cubic geometry to four equivalent Cr and four equivalent Ni atoms. All Ni–Ni bond lengths are 2.44 Å. In the second Ni site, Ni is bonded in a 8-coordinate geometry to six equivalent Cr and eight equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Ni by Materials Project

Cr3Ni is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a distorted body-centered cubic geometry to four equivalent Cr and four equivalent Ni atoms. All Cr–Cr bond lengths are 2.49 Å. All Cr–Ni bond lengths are 2.49 Å. In the second Cr site, Cr is bonded in a 8-coordinate geometry to eight equivalent Cr and six equivalent Ni atoms. All Cr–Ni bond lengths are 2.88 Å. Ni is bonded in a distorted body-centered cubic geometry to fourteen Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Ni by Materials Project

Cr3Ni is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cr is bonded to eight equivalent Cr and four equivalent Ni atoms to form CrCr8Ni4 cuboctahedra that share corners with twelve equivalent CrCr8Ni4 cuboctahedra, edges with eight equivalent NiCr12 cuboctahedra, edges with sixteen equivalent CrCr8Ni4 cuboctahedra, faces with four equivalent NiCr12 cuboctahedra, and faces with fourteen equivalent CrCr8Ni4 cuboctahedra. All Cr–Cr bond lengths are 2.52 Å. All Cr–Ni bond lengths are 2.52 Å. Ni is bonded to twelve equivalent Cr atoms to form NiCr12 cuboctahedra that share corners with twelve equivalent NiCr12 cuboctahedra, edges with twenty-four equivalent CrCr8Ni4 cuboctahedra, faces with six equivalent NiCr12 cuboctahedra, and faces with twelve equivalent CrCr8Ni4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Ni by Materials Project

Cr3Ni is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded to eight equivalent Cr and four equivalent Ni atoms to form CrCr8Ni4 cuboctahedra that share corners with four equivalent CrCr8Ni4 cuboctahedra, corners with eight equivalent NiCr12 cuboctahedra, edges with twenty-four CrCr8Ni4 cuboctahedra, faces with six equivalent NiCr12 cuboctahedra, and faces with twelve CrCr8Ni4 cuboctahedra. All Cr–Cr bond lengths are 2.53 Å. All Cr–Ni bond lengths are 2.54 Å. In the second Cr site, Cr is bonded to eight Cr and four equivalent Ni atoms to form CrCr8Ni4 cuboctahedra that share corners with twelve equivalent CrCr8Ni4 cuboctahedra, edges with eight equivalent NiCr12 cuboctahedra, edges with sixteen CrCr8Ni4 cuboctahedra, faces with four equivalent NiCr12 cuboctahedra, and faces with fourteen CrCr8Ni4 cuboctahedra. All Cr–Cr bond lengths are 2.54 Å. All Cr–Ni bond lengths are 2.53 Å. Ni is bonded to twelve Cr atoms to form NiCr12 cuboctahedra that share corners with four equivalent NiCr12 cuboctahedra, corners with eight equivalent CrCr8Ni4 cuboctahedra, edges with eight equivalent NiCr12 cuboctahedra, edges with sixteen equivalent CrCr8Ni4 cuboctahedra, faces with four equivalent NiCr12 cuboctahedra, and faces with fourteen CrCr8Ni4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr4Ni by Materials Project

Cr4Ni crystallizes in the orthorhombic Fmmm space group. The structure is three-dimensional. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a 8-coordinate geometry to two equivalent Cr and two equivalent Ni atoms. Both Cr–Cr bond lengths are 2.48 Å. Both Cr–Ni bond lengths are 2.46 Å. In the second Cr site, Cr is bonded in a distorted body-centered cubic geometry to eight Cr atoms. There are four shorter (2.44 Å) and two longer (2.50 Å) Cr–Cr bond lengths. Ni is bonded in a 12-coordinate geometry to four equivalent Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrNi3 by Materials Project

Ni3Cr crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Cr is bonded to six equivalent Cr and six equivalent Ni atoms to form CrCr6Ni6 cuboctahedra that share corners with six equivalent CrCr6Ni6 cuboctahedra, corners with six equivalent NiNi12 cuboctahedra, edges with six equivalent CrCr6Ni6 cuboctahedra, edges with eighteen NiCr3Ni9 cuboctahedra, faces with six equivalent CrCr6Ni6 cuboctahedra, and faces with twelve equivalent NiCr3Ni9 cuboctahedra. All Cr–Cr bond lengths are 2.50 Å. All Cr–Ni bond lengths are 2.49 Å. There are five inequivalent Ni sites. In the first Ni site, Ni is bonded to three equivalent Cr and nine Ni atoms to form NiCr3Ni9 cuboctahedra that share corners with twelve equivalent NiCr3Ni9 cuboctahedra, edges with six equivalent CrCr6Ni6 cuboctahedra, edges with eighteen NiCr3Ni9 cuboctahedra, faces with six equivalent CrCr6Ni6 cuboctahedra, and faces with twelve NiCr3Ni9 cuboctahedra. There are six shorter (2.50 Å) and three longer (2.52 Å) Ni–Ni bond lengths. In the second Ni site, Ni is bonded to twelve Ni atoms to form NiNi12 cuboctahedra that share corners with six equivalent CrCr6Ni6 cuboctahedra, corners with six equivalent NiNi12 cuboctahedra, edges with six equivalent CrCr6Ni6 cuboctahedra, edges with eighteen NiCr3Ni9 cuboctahedra, and faces with eighteen NiCr3Ni9 cuboctahedra. All Ni–Ni bond lengths are 2.50 Å. In the third Ni site, Ni is bonded to three equivalent Cr and nine Ni atoms to form NiCr3Ni9 cuboctahedra that share corners with seventeen NiCr3Ni9 cuboctahedra, edges with six equivalent CrCr6Ni6 cuboctahedra, edges with sixteen NiCr3Ni9 cuboctahedra, faces with six equivalent CrCr6Ni6 cuboctahedra, and faces with fifteen NiCr3Ni9 cuboctahedra. All Ni–Cr bond lengths are 2.49 Å. There are six shorter (2.50 Å) and three longer (2.52 Å) Ni–Ni bond lengths. In the fourth Ni site, Ni is bonded to sixteen Ni atoms to form NiNi16 cuboctahedra that share corners with six equivalent CrCr6Ni6 cuboctahedra, corners with sixteen NiCr3Ni9 cuboctahedra, edges with six equivalent CrCr6Ni6 cuboctahedra, edges with eighteen NiCr3Ni9 cuboctahedra, and faces with thirty-four NiCr3Ni9 cuboctahedra. There are a spread of Ni–Ni bond distances ranging from 2.50–5.00 Å. In the fifth Ni site, Ni is bonded to three equivalent Cr and nine Ni atoms to form NiCr3Ni9 cuboctahedra that share corners with seventeen NiCr3Ni9 cuboctahedra, edges with six equivalent CrCr6Ni6 cuboctahedra, edges with sixteen NiCr3Ni9 cuboctahedra, faces with six equivalent CrCr6Ni6 cuboctahedra, and faces with fifteen NiNi16 cuboctahedra. All Ni–Cr bond lengths are 2.49 Å. All Ni–Ni bond lengths are 2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr2Ni by Materials Project

Cr2Ni is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Cr is bonded to six equivalent Cr and six equivalent Ni atoms to form a mixture of edge, corner, and face-sharing CrCr6Ni6 cuboctahedra. All Cr–Cr bond lengths are 2.32 Å. All Cr–Ni bond lengths are 2.72 Å. Ni is bonded in a 12-coordinate geometry to twelve equivalent Cr and four equivalent Ni atoms. All Ni–Ni bond lengths are 2.84 Å.

36 MATERIALS SCIENCE↗