Accession Number : AD0622249

Title :   A STUDY OF THE HAFNIUM-OXYGEN SYSTEM.

Descriptive Note : Interim rept. for May 62-Apr 64,

Corporate Author : IIT RESEARCH INST CHICAGO ILL

Personal Author(s) : Domagala,Robert F. ; Ruh,Robert

Report Date : JUL 1965

Pagination or Media Count : 40

Abstract : A study of annealed and quenched specimens of arcmelted alloys permitted the construction of the binary diagram from Hf to HfO2 and from 700 to 2500C. The diagram is characterized by the following features. (1) Additions of oxygen to Hf raise the alpha-beta (hcp-bcc) transformation temperature (1775 = 25C) resulting in a peritectic reaction L(about 1 a/o O) + alpha (about 8 a/o O) yields beta (about 3 a/o O) at about 2250C. (2) The alpha phase has a broad solubility for oxygen. The maximum solubility has been positioned at 22 a/o O, decreasing to 20 a/o from 2000C. The alpha phase is stabilized to its melting point, 2500C. (3) A eutectic exists where L(about 37 a/o O) yields alpha (about 22 a/o O) + HfO2 at about 2200C. (4) HfO2 has a limited homogeneity range extending from about 66 to 66.7 a/o O. No metallographic evidence of the monoclinic-tetragonal inversion in HfO2 was noted. (5) The lattice parameters of specimens annealed at 1000C indicate a solubility limit for oxygen in alpha at 18.6 a/o, in reasonably good agreement with metallographically determined boundary. (Author)

Descriptors :   (*HAFNIUM ALLOYS, PHASE STUDIES), HAFNIUM, HAFNIUM COMPOUNDS, OXIDES, TRANSITION TEMPERATURE, TRANSFORMATIONS, HARDNESS, MICROSTRUCTURE, HEAT TREATMENT, X RAY DIFFRACTION, CERAMIC MATERIALS

Distribution Statement : APPROVED FOR PUBLIC RELEASE