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All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A Preliminary Investigation of the Cr3Si-Mo Pseudo-Binary Phase Diagram

An investigation was undertaken to study the phase relations in Cr3Si alloyed with Mo varying from 10 to 83.5 wt. % of the material. Specimens were prepared from arc-melted buttons that were subsequently heat treated at 1673 K for 200 h and air quenched to room temperature to structures. Alloys containing more than 20 wt. % MO were primarily two-phase materials of M3Si and M5Si3, where M is (Cr,Mo). Three alloys contained less than 5% of a third phase, which also had the M5Si3 crystal structure. Differential thermal analysis (DTA) was performed on several specimens at temperatures up to 2073 K in order to determine a solidus curve for the M3Si phase. Since only one DTA peak was observed in each alloy, the M5Si3 phase must melt above 2073 K, the maximum temperature examined. A preliminary pseudo-binary phase diagram for (Cr,Mo)3Si and a portion of the 1673 K isothermal section of the Cr-Mo-Si ternary phase diagram are presented.

Dickerson, R. M.↗
NASA NTRS2014

Comparison of the Thermal Expansion Behavior of Several Intermetallic Silicide Alloys Between 293 and 1523 K

Thermal expansion measurements were conducted on hot-pressed CrSi(sub 2), TiSi(sub 2), W Si(sub 2) and a two-phase Cr-Mo-Si intermetallic alloy between 293 and 1523 K during three heat-cool cycles. The corrected thermal expansion, (L/L(sub 0)(sub thermal), varied with the absolute temperature, T, as (deltaL/L(sub 0)(sub thermal) = A(T-293)(sup 3) + B(T-293)(sup 2) + C(T-293) + D, where A, B, C and D are regression constants. Excellent reproducibility was observed for most of the materials after the first heat-up cycle. In some cases, the data from the first heatup cycle deviated from those determined in the subsequent cycles. This deviation was attributed to the presence of residual stresses developed during processing, which are relieved after the first heat-up cycle.

silicides↗
DOE OSTI2020

Materials Data on CrSiMo by Materials Project

CrSiMo crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are two inequivalent Mo2+ sites. In the first Mo2+ site, Mo2+ is bonded in a 5-coordinate geometry to five Si4- atoms. There are a spread of Mo–Si bond distances ranging from 2.73–2.83 Å. In the second Mo2+ site, Mo2+ is bonded in a 7-coordinate geometry to seven Si4- atoms. There are a spread of Mo–Si bond distances ranging from 2.77–2.81 Å. There are two inequivalent Cr2+ sites. In the first Cr2+ site, Cr2+ is bonded in a distorted hexagonal planar geometry to two equivalent Cr2+ and four Si4- atoms. Both Cr–Cr bond lengths are 2.35 Å. There are a spread of Cr–Si bond distances ranging from 2.38–2.42 Å. In the second Cr2+ site, Cr2+ is bonded in a 6-coordinate geometry to four Cr2+ and two equivalent Si4- atoms. There are one shorter (2.35 Å) and one longer (2.48 Å) Cr–Cr bond lengths. There are one shorter (2.40 Å) and one longer (2.49 Å) Cr–Si bond lengths. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded to six Mo2+ and six Cr2+ atoms to form SiCr6Mo6 cuboctahedra that share corners with fourteen SiCr6Mo6 cuboctahedra, edges with six SiCr6Mo6 cuboctahedra, and faces with four equivalent SiCr2Si4Mo6 cuboctahedra. In the second Si4- site, Si4- is bonded to six Mo2+, two equivalent Cr2+, and four Si4- atoms to form distorted SiCr2Si4Mo6 cuboctahedra that share corners with eight SiCr6Mo6 cuboctahedra, edges with two equivalent SiCr2Si4Mo6 cuboctahedra, and faces with ten SiCr6Mo6 cuboctahedra. There are a spread of Si–Si bond distances ranging from 2.40–2.47 Å. In the third Si4- site, Si4- is bonded to six Mo2+, two equivalent Cr2+, and four equivalent Si4- atoms to form distorted SiCr2Si4Mo6 cuboctahedra that share corners with six SiCr6Mo6 cuboctahedra, edges with six SiCr6Mo6 cuboctahedra, and faces with eight equivalent SiCr2Si4Mo6 cuboctahedra.

36 MATERIALS SCIENCE↗