Nucleation and propagation of cracks at grain boundaries in zinc bicrystals

Journal Article · Fri Sep 01 04:00:00 EDT 1989 · Journal of Materials Research; (USA)

DOI:https://doi.org/10.1557/JMR.1989.1182· OSTI ID:5487786

Schmitz, H A ^[1]; Dew-Hughes, D ^[2]; Bilello, J C ^[3]

---

1. Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794 (US)
2. Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, United Kingdom
3. Department of Mechanical Engineering, California State University, Fullerton, California 92634

A study has been made of fatigue and fracture in zinc bicrystals. It is shown that cleavage cracks are nucleated, both under tension and as a result of fatigue, in regions of multiple slip adjacent to grain boundaries at stresses below those for crack nucleation in single crystals. The nature of crack penetration through the boundary is observed as a function of orientation across the boundary. Low angle tilt boundaries are barriers to crack propagation, increasing effective surface energies for crack propagation by 1.6--2 times. Twist boundaries, due to the tearing that accompanies penetration, can result in a twelvefold increase in effective surface energy. Nonbasal cleavage is associated with a twinning mechanism, and an even higher surface energy is required to propagate a crack into a crystal oriented for this type of cleavage. The results carry the implication that, in the absence of surface defects, fatigue failure in polycrystalline zinc is nucleated at the first internal grain boundary and not at the surface.

• OSTI ID: 5487786
• Journal Information: Journal of Materials Research; (USA), Journal Name: Journal of Materials Research; (USA) Vol. 4:5; ISSN JMREE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
BICRYSTALS
CLEAVAGE
CRACK PROPAGATION
CRYSTAL STRUCTURE
CRYSTALS
DEFORMATION
ELEMENTS
ENERGY
FAILURES
FATIGUE
FRACTURES
FREE ENERGY
GRAIN BOUNDARIES
LOW TEMPERATURE
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
MONOCRYSTALS
NUCLEATION
PHYSICAL PROPERTIES
POLYCRYSTALS
SLIP
SURFACE ENERGY
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
TWINNING
ZINC