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9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The growth of metastable peritectic compounds

The effects of directional solidification processing on the microstructural, compositional, and magnetic properties of high-melting-temperature, commercially important alloys which form from the liquid state via peritectic or eutectic type reactions were determined. Emphasis was placed on ferromagnetic compounds of the commercially important Co-Sm and Al-Mn systems. The primary dendrite spacing for eutectic Sm2Co17/Co scaled with negative square root of V and varied from approximately 50 microns for V 20 cm/h to hundreds of microns for V 10 cm/h. Since the crystal growth mechanism was dendritic rather than cooperative, the assoicated permanent magnet properties were rather poor. Magnetization as a function of sample orientation indicates that the easy axis of magnetization was primarily along the direction of solidification for the eutectic Sm2Co17/Co and peritectic SmCo5/Sm2Co17 compositions. For the Al-Mn case, magnetization and microstructural characterization suggest isotropic, polycrystalling growth for all solidification velocities studied.

Pirich, R. G.↗
NASA NTRS1986

Directional solidification and characterization of near eutectic Sm2CO17/Co alloys

The effects of directional solidification processing on the microstructural, compositional, and magnetic properties of near eutectic Co-Sm alloys (about 9 at. pct Sm) have been studied. Initial investigations have been performed at modest thermal gradients in the liquid, G(L) less than 60 C/cm and over a range of furnace (solidification) velocities, V = 0.8 45.4 cm/h. The primary dendrite spacing for near eutectic Sm2Co17/Co scaled with 1/sq rt V and varied from about 50 microns for V greater than or equal to 20 cm/h to hundreds of microns for V less than 10 cm/h, while the rod eutectic diameter and interrod spacing were an order of magnitude smaller. For both dendritic and cooperative growth, the associated permanent magnet properties were rather poor, e.g., remanence less than 4 kG and coercive force less than 1 kOe for the smallest dendrite and rod diameter dimensions encountered, although the magnetic hardness for the rod eutetic was larger than for the dendritic microstructure. Magnetization as a function of sample orientation indicated that the easy axis of magnetization was primarily along the direction of solidification for both ferromagnetic phases.

Pirich, Ronald G.↗
DOE OSTI2020

Materials Data on SmCo5 by Materials Project

SmCo5 crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Sm is bonded in a 6-coordinate geometry to eighteen Co atoms. There are six shorter (2.87 Å) and twelve longer (3.18 Å) Sm–Co bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to three equivalent Sm and six equivalent Co atoms. All Co–Co bond lengths are 2.45 Å. In the second Co site, Co is bonded to four equivalent Sm and eight Co atoms to form a mixture of face, edge, and corner-sharing CoSm4Co8 cuboctahedra. All Co–Co bond lengths are 2.48 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmCo2 by Materials Project

SmCo2 is Cubic Laves structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Sm is bonded in a 12-coordinate geometry to twelve equivalent Co atoms. All Sm–Co bond lengths are 3.01 Å. Co is bonded to six equivalent Sm and six equivalent Co atoms to form a mixture of edge, face, and corner-sharing CoSm6Co6 cuboctahedra. All Co–Co bond lengths are 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm2Co7 by Materials Project

Sm2Co7 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a 12-coordinate geometry to twelve Co atoms. There are a spread of Sm–Co bond distances ranging from 2.90–3.16 Å. In the second Sm site, Sm is bonded in a 6-coordinate geometry to eighteen Co atoms. There are a spread of Sm–Co bond distances ranging from 2.90–3.25 Å. There are five inequivalent Co sites. In the first Co site, Co is bonded to six equivalent Sm and six equivalent Co atoms to form CoSm6Co6 cuboctahedra that share corners with twelve equivalent CoSm5Co7 cuboctahedra, edges with six equivalent CoSm6Co6 cuboctahedra, and faces with eighteen equivalent CoSm5Co7 cuboctahedra. All Co–Co bond lengths are 2.57 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to three equivalent Sm and six Co atoms. There are three shorter (2.43 Å) and three longer (2.46 Å) Co–Co bond lengths. In the third Co site, Co is bonded in a 12-coordinate geometry to three equivalent Sm and six Co atoms. There are three shorter (2.44 Å) and three longer (2.46 Å) Co–Co bond lengths. In the fourth Co site, Co is bonded to four equivalent Sm and eight Co atoms to form CoSm4Co8 cuboctahedra that share corners with sixteen CoSm5Co7 cuboctahedra, edges with ten CoSm5Co7 cuboctahedra, and faces with ten CoSm4Co8 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.52 Å) Co–Co bond lengths. In the fifth Co site, Co is bonded to five Sm and seven Co atoms to form distorted CoSm5Co7 cuboctahedra that share corners with seventeen CoSm6Co6 cuboctahedra, edges with eight CoSm4Co8 cuboctahedra, and faces with fourteen CoSm6Co6 cuboctahedra. There are two shorter (2.50 Å) and two longer (2.52 Å) Co–Co bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm5Co2 by Materials Project

Co2Sm5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Sm sites. In the first Sm site, Sm is bonded in a 2-coordinate geometry to three equivalent Co atoms. There are a spread of Sm–Co bond distances ranging from 2.76–3.22 Å. In the second Sm site, Sm is bonded to four equivalent Co atoms to form distorted edge-sharing SmCo4 tetrahedra. There are two shorter (2.89 Å) and two longer (2.93 Å) Sm–Co bond lengths. In the third Sm site, Sm is bonded in a distorted bent 150 degrees geometry to two equivalent Co atoms. There are one shorter (2.71 Å) and one longer (2.78 Å) Sm–Co bond lengths. Co is bonded in a 7-coordinate geometry to seven Sm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm3Co by Materials Project

Sm3Co is Cementite structured and crystallizes in the orthorhombic Pnma space group. The structure is two-dimensional and consists of two Sm3Co sheets oriented in the (0, 0, 1) direction. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a bent 150 degrees geometry to two equivalent Co atoms. There are one shorter (2.73 Å) and one longer (2.85 Å) Sm–Co bond lengths. In the second Sm site, Sm is bonded in a distorted water-like geometry to two equivalent Co atoms. There are one shorter (2.78 Å) and one longer (2.88 Å) Sm–Co bond lengths. Co is bonded in a 6-coordinate geometry to six Sm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sm2Co17 by Materials Project

Sm2Co17 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Sm sites. In the first Sm site, Sm is bonded in a 12-coordinate geometry to eighteen Co atoms. There are a spread of Sm–Co bond distances ranging from 2.98–3.27 Å. In the second Sm site, Sm is bonded in a 2-coordinate geometry to twenty Co atoms. There are a spread of Sm–Co bond distances ranging from 2.91–3.16 Å. There are four inequivalent Co sites. In the first Co site, Co is bonded in a 2-coordinate geometry to one Sm and thirteen Co atoms. There are a spread of Co–Co bond distances ranging from 2.32–2.66 Å. In the second Co site, Co is bonded to two equivalent Sm and ten Co atoms to form CoSm2Co10 cuboctahedra that share corners with twenty-two CoSm2Co10 cuboctahedra, edges with ten CoSm3Co9 cuboctahedra, and faces with eighteen CoSm2Co10 cuboctahedra. There are four shorter (2.40 Å) and four longer (2.42 Å) Co–Co bond lengths. In the third Co site, Co is bonded to two Sm and ten Co atoms to form a mixture of distorted edge, face, and corner-sharing CoSm2Co10 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.34–2.58 Å. In the fourth Co site, Co is bonded to three Sm and nine Co atoms to form a mixture of distorted edge, face, and corner-sharing CoSm3Co9 cuboctahedra. Both Co–Co bond lengths are 2.44 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmCo12 by Materials Project

SmCo12 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Sm is bonded to twelve Co atoms to form face-sharing SmCo12 cuboctahedra. There are four shorter (2.71 Å) and eight longer (2.91 Å) Sm–Co bond lengths. There are three inequivalent Co sites. In the first Co site, Co is bonded in a 4-coordinate geometry to two equivalent Sm and twelve Co atoms. There are a spread of Co–Co bond distances ranging from 2.40–2.93 Å. In the second Co site, Co is bonded in a 12-coordinate geometry to eleven Co atoms. There are a spread of Co–Co bond distances ranging from 2.26–2.60 Å. In the third Co site, Co is bonded in a 5-coordinate geometry to one Sm and ten Co atoms. Both Co–Co bond lengths are 2.23 Å.

36 MATERIALS SCIENCE↗