X-ray topographic fractography of single crystals of molybdenum and niobium

Technical Report · Wed Dec 01 00:00:00 EST 1982

OSTI ID:6601785

Hmelo, A B

The semi-brittle (001) cleavage fracture at 77/sup 0/K of Mo and outgassed Nb single crystals was related to their fracture toughness. Berg-Barrett x-ray reflection topography and White Beam Synchrotron Fractography were used. Calibrated electropolishing in layers followed by Synchrotron Fractography revealed that under the conditions which existed at the tip of the running crack, Mo underwent general yielding which resulted in a plastically curved lattice. This result correlates with the substantial fracture toughness for Mo measured previously. On the other hand, double (112) slip was observed for Nb. The plastic zone associated with the crack-tip is shown to have a structure typicla of shock-loaded materials, consisting of arrays of screw dislocations, micro- and macrotwins. This result correlates with the low fracture toughness of Nb at 77/sup 0/K. It is proposed that these extremes in cleavage behavior for Mo vs Nb can be rationalized in terms of the capacity of a bcc structure to undergo a slip to twinning transition at high strain rates. 32 figures, 5 tables.

• Research Organization: State Univ. of New York, Stony Brook (USA). Dept. of Materials Science and Engineering
• DOE Contract Number: AC02-80ER10740
• OSTI ID: 6601785
• Report Number(s): DOE/ER/10740-8; ON: DE83005066
• Resource Relation: Other Information: Thesis
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MOLYBDENUM
FRACTURE PROPERTIES
NIOBIUM
CRACKS
DEFORMATION
ELECTROPOLISHING
LOW TEMPERATURE
MONOCRYSTALS
REFLECTION
SYNCHROTRON RADIATION
TOPOGRAPHY
X RADIATION
BREMSSTRAHLUNG
CRYSTALS
ELECTROLYSIS
ELECTROMAGNETIC RADIATION
ELEMENTS
IONIZING RADIATIONS
LYSIS
MECHANICAL PROPERTIES
METALS
POLISHING
RADIATIONS
SURFACE FINISHING
TRANSITION ELEMENTS
360103* - Metals & Alloys- Mechanical Properties