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Non-octahedral slip in aluminum
238
ACTA
METALLURGICA,
show that the crystal has a continuous twist about [OOl] axis. Annealing for 7 hours at 330°C did not result in any noticeable change in the pattern. After annealing for 7 hours at 720°C (Fig. 3), it was found that the region (a) disappeared completely and the region (b) changed into several reflection lines. This indicates that the continuous twist has been replaced by discontinuous boundary separating small crystallites. The reflection patterns for various orientations and locations of the crystal show that these boundaries lie on an undulating surface which is nearly (OOl)plane. The author has also examined the rotation angles about the [lOO] and [OlO] axis, and has observed that these are very small. This means that the grainboundary is a twisting boundary though it is not the pure twist boundary introduced by Burgers,t4) Frank,c6) and Van der Merwe.t6) Before annealing, excess dislocations of the screw type are inferred to be distributed at random in both regions (a) and (b). The force between parallel screw dislocations of the same sign is repulsive, while that between perpendicular dislocations is attractive. Therefore, the perpendicular dislocations approach closely to one another cn annealing, and become arranged into a grid. This phenomenon is similar to the well-known polygonization(7) in a bent crystal. The author expresses his appreciation to Prof. A. Ookawa for his helpful discussions and to Prof. R. Uyeda for his kind advice. NORIO KATO
Kobayasi Institute of Physical Kokubunji, Tokyo, Japan
Research
References 1, H. LAMBOT,L. VASSAMILLET,and J. DEJACE Acta Met. 1, 711 (1963); ibid. 3, 150 (1955). 2. Y. CAUCHOIS J. Phys. Radium 3, 320 (1932). 3. H. S. PEISER,H. ROOKSBY,and A. J. C. WILSON X-ray Diflraction by PoEycrystallineMate&& (London, 1955) D. 128. H. WELSDORF NatumGs. 58. 250 11954). 4. 5. M. BURNERS Proc. Phya. Sot. 59.23 (1940). 6. F. C. FRANK The Strength of Solids (London, Physical Society, 1948), p. 46.
VOL.
5,
1957
6. J. H. VAN DERMERWE Proc. Phye. Sot. A63,616 (1950). 7. R. W. CAHN J. Inst. Metals 76, 121 (1949). * Received October 27, 1956; in revised form October 31, 1956.
Non-octahedral
Slip in Aluminum*
In a recent note(l) the undersigned have reported the occurrence of non-octahedral slip in aluminum bicrystals and tricrystals deformed in tension at room temperature. The results of a one-surface stereographic analysis suggested that the nonoctahedral slip took place on {llO}- and {331}-type planes and was induced by slip on octahedral planes in the adjacent crystal. This was thought to have happened when a similarly oriented acting octahedral slip plane in an adjacent crystal induced slip on a non-octahedral plane across the grain-boundary. Further work was carried out on a tricrystal of an orientation similar to that indicated in the previous note(l). As before, the specimen was deformed in tension at room temperature. In this case, by appropriately shaping the sample, it was possible to carry out a two-surface stereographic analysis of one of the acting non-octahedral slip systems. This system was found to be of the (221) type. Again, the orientation relationships were such that non-octahedral slip could have been induced by octahedral slip in the neighboring grain. It is, therefore, suggested that slip on planes of the {hhl) type can be induced across a grainboundary by octahedral slip in an adjacent grain, when the two systems are similarly oriented and the position of the grain-boundary is favorable for such a process. T. OJALA University of Toronto C. ELBAUM Toronto, Ont. W. C. WINEGARD References 1. T. OJALA, C. ELBAUM, and W. C. WINECUED J. Metala (Transaction Section) 8, 1344 (1956). * Received November 8, 1966.
ACTA
METALLURGICA,
show that the crystal has a continuous twist about [OOl] axis. Annealing for 7 hours at 330°C did not result in any noticeable change in the pattern. After annealing for 7 hours at 720°C (Fig. 3), it was found that the region (a) disappeared completely and the region (b) changed into several reflection lines. This indicates that the continuous twist has been replaced by discontinuous boundary separating small crystallites. The reflection patterns for various orientations and locations of the crystal show that these boundaries lie on an undulating surface which is nearly (OOl)plane. The author has also examined the rotation angles about the [lOO] and [OlO] axis, and has observed that these are very small. This means that the grainboundary is a twisting boundary though it is not the pure twist boundary introduced by Burgers,t4) Frank,c6) and Van der Merwe.t6) Before annealing, excess dislocations of the screw type are inferred to be distributed at random in both regions (a) and (b). The force between parallel screw dislocations of the same sign is repulsive, while that between perpendicular dislocations is attractive. Therefore, the perpendicular dislocations approach closely to one another cn annealing, and become arranged into a grid. This phenomenon is similar to the well-known polygonization(7) in a bent crystal. The author expresses his appreciation to Prof. A. Ookawa for his helpful discussions and to Prof. R. Uyeda for his kind advice. NORIO KATO
Kobayasi Institute of Physical Kokubunji, Tokyo, Japan
Research
References 1, H. LAMBOT,L. VASSAMILLET,and J. DEJACE Acta Met. 1, 711 (1963); ibid. 3, 150 (1955). 2. Y. CAUCHOIS J. Phys. Radium 3, 320 (1932). 3. H. S. PEISER,H. ROOKSBY,and A. J. C. WILSON X-ray Diflraction by PoEycrystallineMate&& (London, 1955) D. 128. H. WELSDORF NatumGs. 58. 250 11954). 4. 5. M. BURNERS Proc. Phya. Sot. 59.23 (1940). 6. F. C. FRANK The Strength of Solids (London, Physical Society, 1948), p. 46.
VOL.
5,
1957
6. J. H. VAN DERMERWE Proc. Phye. Sot. A63,616 (1950). 7. R. W. CAHN J. Inst. Metals 76, 121 (1949). * Received October 27, 1956; in revised form October 31, 1956.
Non-octahedral
Slip in Aluminum*
In a recent note(l) the undersigned have reported the occurrence of non-octahedral slip in aluminum bicrystals and tricrystals deformed in tension at room temperature. The results of a one-surface stereographic analysis suggested that the nonoctahedral slip took place on {llO}- and {331}-type planes and was induced by slip on octahedral planes in the adjacent crystal. This was thought to have happened when a similarly oriented acting octahedral slip plane in an adjacent crystal induced slip on a non-octahedral plane across the grain-boundary. Further work was carried out on a tricrystal of an orientation similar to that indicated in the previous note(l). As before, the specimen was deformed in tension at room temperature. In this case, by appropriately shaping the sample, it was possible to carry out a two-surface stereographic analysis of one of the acting non-octahedral slip systems. This system was found to be of the (221) type. Again, the orientation relationships were such that non-octahedral slip could have been induced by octahedral slip in the neighboring grain. It is, therefore, suggested that slip on planes of the {hhl) type can be induced across a grainboundary by octahedral slip in an adjacent grain, when the two systems are similarly oriented and the position of the grain-boundary is favorable for such a process. T. OJALA University of Toronto C. ELBAUM Toronto, Ont. W. C. WINEGARD References 1. T. OJALA, C. ELBAUM, and W. C. WINECUED J. Metala (Transaction Section) 8, 1344 (1956). * Received November 8, 1966.