Accession Number : ADA305717

Title :   Advanced MoSi2 Compositions.

Descriptive Note : Final rept. 15 Jul 92-14 Dec 95,

Corporate Author : UNITED TECHNOLOGIES RESEARCH CENTER EAST HARTFORD CT

Personal Author(s) : Chin, S. ; Anton, D. L. ; Giamei, A. F.

PDF Url : ADA305717

Report Date : 16 FEB 1996

Pagination or Media Count : 86

Abstract : Single-phase and two-phase MoSi2 and MoSi2 alloys modified with Al, B, Ge, Hf, Nb and Re have been investigated. B and Hf were found to exhibit no appreciable solubility in MoSi2 and were not considered for further evaluation. Alloys with Al & Nb substitutions for Si and Mo, respectively, have the hexagonal C40 crystal structure. Alloys with Ge and Re substitutions for Si and Mo, respectively, maintained the tetragonal C11b crystal structure. Two-phase alloys modified with Nb and exhibiting the C40 + C11b crystal structure were also evaluated. Additionally, MoSi2 with the C40 structure containing Nb+Re were evaluated. The mechanical properties were evaluated using the following tests: four-point flexure testing to determine strength, ductility, modulus, and ductile-to-brittle transition temperature (DBTT); three-point notched K( sub ic) flexure testing to detemine fracture toughness; compression testing to determine compressive yield strength, and compressive creep testing. Flexural testing indicate a DBTT of 1250-1350 deg C for the baseline MoSi2 and all of the modifications evaluated. Several of the Nb and/or Re modified alloys were found to exhibit a good combination of mechanical properties. The oxidation resistance of MoSi2 was not significantly altered with all of the alloy modifications evaluated. Various atomic modeling tools were evaluated to visualize bonding in MoSi2. jg p2

Descriptors :   *COMPOSITE MATERIALS, *SILICIDES, *MOLYBDENUM ALLOYS, TEST AND EVALUATION, MECHANICAL PROPERTIES, HAFNIUM, MODIFICATION, TEST METHODS, TOUGHNESS, PHASE STUDIES, FRACTURE(MECHANICS), DUCTILE BRITTLE TRANSITION, TRANSITION TEMPERATURE, ALUMINUM, NIOBIUM, YIELD STRENGTH, SOLUBILITY, BORON, COMPRESSIVE STRENGTH, GERMANIUM, FLEXURAL PROPERTIES, COMPRESSIVE PROPERTIES, CREEP TESTS, INTERMETALLIC COMPOUNDS, RHENIUM, ARC MELTING.

Subject Categories : Inorganic Chemistry
      Properties of Metals and Alloys
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE