Abstract
Direct observations were made of the propagation of ductile cracks and associated dislocation behaviour at crack tips in aluminium during tensile deformation in an electron microscope. In the electropolished area, the cracks propagated as a Mode III shear-type by emitting screw dislocations on a plane coplanar to the crack plane. A zone free of dislocations was observed between the crack tip and the plastic zone. As the cracks propagated into thicker areas, the fracture mode changed from Mode III to predominantly Mode I. The crack top of the Mode I cracks was blunted by emitting edge dislocations on planes inclined to the crack plane. The blunted cracks did not propagate until the area ahead of the crack tip was sufficiently thinned by plastic deformation. The cracks then propagated abruptly, apparently without emitting dislocations. The stress intensity factor was measured from the crack tip geometry of Mode III cracks and it was found to be in good agreement with the critical value of the stress intensity factor required for dislocation generation.
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References
J. Narayan andS. M. Ohr, Proceedings 9th International Congress on Electron Microscopy, Vol. 1, edited by J. M. Sturgess (1978) p. 580.
S. Kobayashi andS. M. Ohr, Proceedings 37th Annual Meeting of EMSA, edited by G. W. Bailey (1979) p. 424.
S. M. Ohr andJ. Narayan,Phil. Mag. A41 (1980) 81.
S. Kobayashi andS. M. Ohr,ibid. A42 (1980) 763.
S. M. Ohr andS. Koyayashi,J. Metals 32 (1980) 35.
S. Kobayashi andS. M. Ohr,Scripts Met. 15 (1981) 343.
B. A. Bilby, A. H. Cottrell andK. H. Swinden,Proc. R. Soc. A272 (1963) 304.
S. J. Chang andS. M. Ohr, in “Dislocation Modelling of Physical Systems”, edited by M. F. Ashby, R. Bullough, C. S. Hartley and J. P. Hirth (Pergamon Press, New York, 1981) p. 23.
S. -J. Chang andS. M. Ohr,J. Appl. Phys. 52 (1981) 7174.
J. J. Gilman,J. Met. 9 (1957) 449.
A. H. Cottrell,Proc. R. Soc. A285 (1965) 10.
R. N. Gardner, T. C. Pollock andH. G. F. Wilsdorf,Mater. Sci. Eng. 29 (1977) 169.
T. Imura, Proceedings of the US-Japan Seminar on New Applications and Extensions of the Unique Advantages of HVEM for Physical and Materials Research, University of Hawaii, Honolulu (1976).
H. G. F. Wilsdorf andD. Kuhlmann-Wils-Dorf,Norelco Reporter 5 (1958) 9.
J. A. Horton, Proceedings of the 40th Annual Meeting of EMSA, edited by G. W. Bailey (1982) in press.
B. A. Bilby andK. H. Swinden,Proc. R. Soc. A285 (1965) 22.
V. Vitek,J. Mech. Phys. Solids 24 (1976) 263.
H. Reidel,ibid 24 (1976) 277.
J. R. Rice andR. Thomson,Phil. Mag. 29 (1974) 73.
J. A. Horton, S. M. Ohr andW. A. Jesser,J. Nucl. Mater. in press.
F. Prinz, H. P. Karnthaler andH. O. K. Kirchner,Acta Met. 29 (1981) 1029.
D. D. Mason,Phil. Mag. A39 (1979) 455.
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Horton, J.A., Ohr, S.M. TEM observations of dislocation emission at crack tips in aluminium. J Mater Sci 17, 3140–3148 (1982). https://doi.org/10.1007/BF01203476
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DOI: https://doi.org/10.1007/BF01203476