Accession Number : AD0698473

Title :   X-RAY AND NEUTRON DIFFRACTION STUDIES OF METALS AND ALLOYS.

Descriptive Note : Final rept. 1 Jan 66-30 Aug 69,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE

Personal Author(s) : Shoemaker,David P.

Report Date : 01 DEC 1969

Pagination or Media Count : 12

Abstract : X-ray crystal structure work on the M phase Nb-Ni-Al, was completed. This orthorhombic structure (Pnam, 52 atoms) shows close relationships to the P and nu phases. The crystal structure of the nu phase, Mn81.5Si18.5, was determined and refined to a high degree of precision. This is the most complex structure yet determined in this program, having 186 atoms in an orthorhombic unit cell (Immm). This structure, too, is closely related to the P phase. A third orthorhombic structure (Pnnm, 74 atoms) has been determined for the Q (X, Y) phase in Mn-Co-Cr. A rough trial structure was obtained for the monoclinic K phase, Fe-Mn-Si. The structures of the monoclinic I phase (V-Ni-Si) and the S phase (Mn-Co-Si) are probably identical. A new scheme for coding layered tetrahedrally close-packed structures was developed. Reinterpretation of polarized-beam neutron diffraction data for 85% ordered VFe, 46.7 at % Fe, has given an improved value for the Fe spin, S sub Fe = 0.368 plus or minus .024; the spin on the vanadium is zero within experimental error. Previous indications of a highly aspherical 3d shell on ion were not substantiated. Attempts to prepare single crystals of sigma CoV for polarized beam single crystal neutron studies were unsuccessful. (Author)

Descriptors :   (*GRAIN STRUCTURES(METALLURGY), DIFFRACTION ANALYSIS), (*X RAY DIFFRACTION, PHASE STUDIES), (*NEUTRON DIFFRACTION, PHASE STUDIES), CRYSTAL STRUCTURE, PHASE STUDIES, NIOBIUM ALLOYS, NICKEL ALLOYS, ALUMINUM ALLOYS, MANGANESE ALLOYS, SILICON ALLOYS, COBALT ALLOYS, CHROMIUM ALLOYS, IRON ALLOYS

Subject Categories : Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE