Accession Number : AD0476759

Title :   INVESTIGATION INTO THE TUNGSTEN-RICH REGION OF THE TUNGSTEN-SILICON SYSTEM AND INTO RELATED METAL-SILICON SYSTEMS.

Descriptive Note : Summary technical rept. for 1 Mar 63-31 Mar 65,

Corporate Author : B S A GROUP RESEARCH CENTRE BIRMINGHAM (UNITED KINGDOM)

Personal Author(s) : Goldschmidt, H. J. ; Catherall, E. A. ; Taylor, R. A.

Report Date : OCT 1965

Pagination or Media Count : 67

Abstract : The solid solubility of Si in W, Mo, Nb and Ta as a function of temperature, and the nature of the metal richest compounds occurring have been determined by X-ray analyses and allied techniques. The solid solutions are found to be substitutional and the lattice contractions with Si content are presented. The maximum solubilities are: W-Si, 1.7 at 2060 C; Mo-Si, 9.0 at 1860 C; Ta-Si, 2.2 at 2310 C; Nb-Si, 3.6 at 1880 C. Si within the solution range increases the hardness of W, Mo, Nb and Ta. The solubilities decrease with decreasing temperature, the most for Mo-Si. Age-hardening is thus possible and has been observed in W-Si at 800 and 1000 C. The metal-richest compounds formed, determined by X-ray diffraction and electron probe analysis, are W5Si3, Mo3Si, Nb3Si and Ta3Si. W3Si of a beta-W type structure has not been observed and this is discussed in the light of the occurrence of beta-W type phases within the periodic system. It is also suggested that ideas about W3O (beta-W proper) should be revised. W5Si3 possesses a homogeneity range towards, but not including W3Si2. Si expands the W5Si3 lattice. The oxidation resistance at 1000 C of W-Si alloys shows marked differences; and attempt is made to explain these in terms of structure and oxide constitution. The melting points determined between W and W5Si3 show a eutectic at 22.6 at.-% Si and 2060 C. (Author)

Descriptors :   (*SILICON ALLOYS, PHASE STUDIES), (*TUNGSTEN ALLOYS, PHASE STUDIES), (*MOLYBDENUM ALLOYS, PHASE STUDIES), (*NIOBIUM ALLOYS, PHASE STUDIES), (*TANTALUM ALLOYS, PHASE STUDIES), SOLID SOLUTIONS, TRANSITION METALS, SOLUBILITY, HARDNESS, EUTECTICS, MELTING POINT, OXIDATION, CRYSTAL LATTICES, CHEMICAL ANALYSIS, SILICIDES, CRYSTAL STRUCTURE, INTERMETALLIC COMPOUNDS, X RAY DIFFRACTION, MICROANALYSIS, PROBES.

Subject Categories : Properties of Metals and Alloys
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE