HVEM observation of dislocation-free zones at crack tips in iron single crystals

Abstract The distribution of dislocations in the vicinity of a crack tip has been studied in single crystals of iron during in situ tensile deformation in a high-voltage electron microscope. The results show that a large number of dislocations are emitted from the crack tip during crack propagation in thick specimens. The emitted dislocations immediately move away from the crack tip, creating a dislocation-free zone (DFZ) near the crack tip. The dislocations come to rest in a plastic zone located some distance from the crack tip and form dense tangles. These observations are discussed in terms of the model of elastic interaction between a crack and dislocations.

[1]  S. Ohr.  An electron microscope study of crack tip deformation and its impact on the dislocation theory of fracture , 1985 .

[2]  S. Burns,et al.  Crack tip deformation in LiF single crystals , 1984 .

[3]  J. Horton,et al.  TEM observations of dislocation emission at crack tips in aluminium , 1982 .

[4]  S. Chang,et al.  Dislocation‐free zone model of fracture comparison with experiments , 1982 .

[5]  S. Dai,et al.  Dislocation-free zone at the crack tip , 1982 .

[6]  S. Chang,et al.  Dislocation-free zone model of fracture , 1981 .

[7]  B. Majumdar,et al.  Crack tip shielding--an elastic theory of dislocations and dislocation arrays near a sharp crack , 1981 .

[8]  S. Kobayashi,et al.  In situ fracture experiments in b.c.c. metals , 1980 .

[9]  Johannes Weertman,et al.  Fracture mechanics: A unified view for Griffith-Irwin-Orowan cracks , 1978 .

[10]  Hiroyasu Saka,et al.  Direct Measurement of Mobility of Edge and Screw Dislocations in 3% Silicon-Iron by High Voltage Transmission Electron Microscopy , 1972 .

[11]  H. Saka,et al.  Direct Observation of Multiplication of Dislocations in Iron Single Crystal by High Voltage Electron Microscopy (HVEM) , 1970 .

[12]  A. Cottrell,et al.  The spread of plastic yield from a notch , 1963, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[13]  J. D. Eshelby,et al.  CXL. Dislocations in thin plates , 1951 .

[14]  R. Thomson.  Brittle fracture in a ductile material with application to hydrogen embrittlement , 1978 .

[15]  James R. Rice,et al.  Ductile versus brittle behaviour of crystals , 1974 .

[16]  H. Saka,et al.  Measurement of the Stress and Strain on Specimens in an Electron Microscope , 1971 .