Accession Number : AD0865809

Title :   Research and Development of Refractory Oxidation-Resistant Diborides. Part II, Volume IV: Mechanical Properties.

Descriptive Note : Technical rept. 15 Sep 67-15 May 69,

Corporate Author : MANLABS INC CAMBRIDGE MA

Personal Author(s) : Rhodes, William H. ; Clougherty, Edward V. ; Kalish, David

Report Date : JAN 1970

Pagination or Media Count : 153

Abstract : Hot pressed diboride compositions of ZrB2 or HfB2 with additions of SiC and/or C were employed to produce materials with a range of compositions and microstructural variations of porosity and grain size for mechanical property evaluations which included ben strength and elastic modulus from room temperature to 1800 and 2100C, respectively; deformation characteristics from 1800 to 2200C, short time compressive creep from 1000 to 1800C and a limited stress-rupture time data at 1040C. All data except the stress-rupture tests were obtained from measurements in either vacuum or inert atmosphere; the stress-rupture tests were conducted in air. Bend strengths were consistent for a specific microstructure and composition; values ranged from 45,000 to 90,000 psi at temperatures up to 800C; 20,000 to 40,000 psi up to 1900C. Bend strength data were analyzed for effects of residual elastic strain, grain size and porosity. Macroscopic deformation was observed above 1600C for a dense 4 micron grain size ZrB2 composition containing C and SiC additives. Creep rates are inversely proportional to grain size and flow stresses are proportional to strain rate to the 0.4 power. Strain hardening was observed at elevated temperatures for several diboride materials containing SiC and/or C. (Author)

Descriptors :   *REFRACTORY MATERIALS, *BORIDES, *ATMOSPHERE ENTRY, MECHANICAL PROPERTIES, SILICON CARBIDES, CARBON, ZIRCONIUM COMPOUNDS, HAFNIUM COMPOUNDS, OXIDATION, MICROSTRUCTURE, DEFORMATION.

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE