Accession Number : AD0271663

Title :   DISLOCATION SOURCES AND THE STRENGTH OF MAGNESIUM OXIDE SINGLE CRYSTALS

Corporate Author : HONEYWELL RESEARCH CENTER HOPKINS MINN

Personal Author(s) : STOKES,R.J.

Report Date : JAN 1962

Pagination or Media Count : 1

Abstract : The report compares the room temperature mechanical behavior of MgO crystals containing fresh and grown in dislocation sources. Fresh dislocation sources introduced by cleavage or mechanical contact move and multiply to generate slip bands at 3000 psi. Macroscopically the crystals yield smoothly at 6000 psi and can be quite ductile. When fresh sources are eliminated by chemical polishing the crystals have to rely on grown in sources to initiate slip. They then deform elastically up to extremely high stresses, about 30,000 to 50,000 psi, yielding with a sharp yield drop down to the stress level at which fresh sources operate. Grown in sources are considered to be associated with impurity precipitate particles or inclusions. Annealing polished crystals at 2000 C dissolves these particles thereby eliminating sources for slip. The crystals then become greater than 70,000 psi and approach within 1/10 of the theoretical strength. (Author)

Descriptors :   *ELASTIC PROPERTIES, *MAGNESIUM COMPOUNDS, *SINGLE CRYSTALS, CRYSTAL LATTICES, CRYSTAL STRUCTURE, CRYSTALS, DEFLECTION, DEFORMATION, DUCTILITY, HEAT TREATMENT, IMPURITIES, LOAD DISTRIBUTION, MECHANICAL PROPERTIES, MICROSTRUCTURE, OXIDES, PHOTOGRAPHIC ANALYSIS, SHEAR STRESSES, SHOCK WAVES, SOLID STATE PHYSICS, SOURCES, TENSILE PROPERTIES

Distribution Statement : APPROVED FOR PUBLIC RELEASE