THE MECHANICAL BEHAVIOR OF MAGNESIUM OXIDE AT HIGH TEMPERATURES

Technical Report · Wed Jan 01 04:00:00 EST 1964

OSTI ID:4069238

Day, R B; Stokes, R J

Magnesium oxide crystals show a wide variety of deformation and fracture modes under tension at high temperatures. These modes are determined by the number of slip systems operating concurrently in a given volume. (i) At low temperatures slip is confined to a single <110> {110} system and plasticity is limited by stress concentrations which develop where slip switches from one plane to another. (ii) At intermediate temperatures <110> {110} slip systems at 90 deg to each other can interpenetrate but those at 60 deg cannot. Mechanical properties then depend on initial slip distribution. When slip is confined to two 90 deg systems there is little work hardening before crystals neck down to a knife edge ductile fracture. When slip is confined to 60 deg systems crystals work harden and fracture by cleavage. (iii) At high temperatures dislocations can interpenetrate on all systems and polygonization can occur. After easy glide the crystals work harden and elongate over 100 percent before fracturing in a completely ductile manner. The transition from one mode to another depends on strain rate. The relative ability for 90 deg or 60 deg systems to intersect is discussed in terms of dislocation interactions. (auth)

• Research Organization: honeywell Research Center, Hopkins, Minn.
• NSA Number: NSA-18-016472
• OSTI ID: 4069238
• Report Number(s): HR-64-253; AD-431615
• Country of Publication: United States
• Language: English

Related Subjects

CRYSTALS
DEFORMATION
DISTRIBUTION
DUCTILITY
FAILURES
HIGH TEMPERATURE
LATTICES
LOW TEMPERATURE
MAGNESIUM OXIDES
MECHANICAL PROPERTIES
METALS, CERAMICS, AND OTHER MATERIALS
SLIP
STRESSES
TEMPERATURE
TEMPERING