INVESTIGATION INTO THE TUNGSTEN-RICH REGION OF THE TUNGSTEN-SILICON SYSTEM AND INTO RELATED METAL-SILICON SYSTEMS.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1965
- Accession Number
- AD0476759
Entities
People
- E. A. Catherall
- H. J. Goldschmidt
- R. A. Taylor