Influence of hydrides on ductile fracture in the Zr-2. 5 Nb alloy
- Moscow Institute of Steel and Alloys, Moscow (Russian Federation)
- Institute of Inorganic Materials, Moscow (Russian Federation)
The influence of hydrides on the mechanism and kinetics of ductile fracture in the Zr-2.5 Nb alloy has been analyzed as a function of static tension of specimens containing 200 ppm hydrogen. The smooth cylindrical specimens used were of two orientations with the maximum hydride platelet dimensions from 5 to 200 [mu]m preferentially oriented parallel to the tensile axis. Nucleation of cracks in hydrides and internal cracks in a specimen at different deformation stages have been studied by recording the peak amplitudes of acoustic emission with a nonresonant damped sensor. The joint analysis of the stress-strain diagrams and acoustic emission results of metallographic and fractographic examinations has revealed the role of hydrides in the loss of stability by flow, neck formation and ductile fracturing under tension. Depending on the length of hydrides, two types of the ductile fracture kinetics are realized. Fine hydrides whose average size is 10 to 20 [mu]m do not influence the stability of the plastic flow under tension, but they merely accelerate the generation of voids at the stage of ductile fracture formation. In contrast, crack nucleation is large hydrides whose average size is [gt]60 to 100 [mu]m is the cause of premature localization of deformation in the neck and axial decohesion in the fracture, which reduces the overall ductility of the alloy. The record of acoustic emission provided by a damped sensor shows that the signal peak amplitude and the axial crack area are proportional; this allows one to use an amplitude analysis of signals for the quantitative estimation of the dimensions of hydride-induced cracks.
- OSTI ID:
- 6007191
- Journal Information:
- Nuclear Science and Engineering; (United States), Journal Name: Nuclear Science and Engineering; (United States) Vol. 115:3; ISSN NSENAO; ISSN 0029-5639
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
220200 -- Nuclear Reactor Technology-- Components & Accessories
36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ACOUSTIC EMISSION TESTING
ACOUSTIC TESTING
ALLOYS
CRACKS
DEFORMATION
DUCTILITY
EMBRITTLEMENT
FRACTURE PROPERTIES
HYDRIDES
HYDROGEN COMPOUNDS
HYDROGEN EMBRITTLEMENT
MATERIALS
MATERIALS TESTING
MECHANICAL PROPERTIES
NIOBIUM ALLOYS
NONDESTRUCTIVE TESTING
REACTOR MATERIALS
TENSILE PROPERTIES
TESTING
VOIDS
ZIRCONIUM ALLOYS
ZIRCONIUM BASE ALLOYS