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Transformation–dislocation dipoles in Laves phases: A high-resolution transmission electron microscopy analysis

Published online by Cambridge University Press:  31 January 2011

J. Aufrecht ,
A. Leineweber ,
V. Duppel  and
E.J. Mittemeijer
A. Leineweber*
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany
V. Duppel
Affiliation:
Max Planck Institute for Solid State Research, D-70569 Stuttgart, Germany
E.J. Mittemeijer
Affiliation:
Max Planck Institute for Metals Research, D-70569 Stuttgart, Germany; and Institute for Materials Science, University of Stuttgart, D-70569 Stuttgart, Germany
*
a)Address all correspondence to this author. e-mail: a.leineweber@mf.mpg.de
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Abstract

Images of synchro-Shockley partial dislocation arrangements in the Laves phases NbCr2 and HfCr2 have been obtained by high-resolution transmission electron microscopy. The analysis of the stacking sequences around these arrangements revealed the role of the constituting partial dislocations in enabling the polytypic C14 → C36/6H phase transformation in both alloys. The synchro-Shockley partial dislocations occur in and move through the crystals mainly as dipoles of partials of opposite signs, leading to—as compared to isolated partials—strain fields of lesser extent. In NbCr2 a single, probably quenched synchro-Shockley partial dislocation dipole, consisting of two partials with Burgers vectors of opposite sign, was identified. The ordered passage of a series of this type of line defects brings about the C14 → C36 transformation. In HfCr2 a complex synchro-Shockley partial dislocation configuration was revealed. It can be regarded as an “antiphase boundary” between two C36 domains. It is likely that this defect structure had formed by impingement of two domains of C36 growing perpendicular to the stacking direction by glide of synchro-Shockley partial dislocation dipoles.

Keywords

Transmission Electron Microscopy (TEM)DislocationsPhase Transformation

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Articles
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Journal of Materials Research , Volume 25 , Issue 10 , October 2010 , pp. 1983 - 1991
Copyright
Copyright © Materials Research Society 2010

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References

REFERENCES

1.Stein, F., Palm, M., Sauthoff, G.Structure and stability of Laves phases part II—Structure type variations in binary and ternary systems. Intermetallics 13, 1056 (2005)CrossRefGoogle Scholar
2.Allen, C.W., Delavignette, P., Amelinckx, S.Electron-microscopic studies of Laves phases TiCr2 and TiCo2. Phys. Status Solidi A 9, 237 (1972)CrossRefGoogle Scholar
3.Nishiyama, Z.Martensitic Transformations (Academic Press, New York 1978)Google Scholar
4.Kitano, Y., Takata, M., Komura, Y.High-resolution electron microscopy of partial dislocations in the Laves phase structure. J. Microsc. 142, (2)181 (1986)CrossRefGoogle Scholar
5.Liu, Y., Livingstone, J.D., Allen, S.M.Defect structures and nonbasal slip of C36 Laves phase MgNi2 in a 2-phase alloy. Metall. Mater. Trans. A 26, 1441 (1995)CrossRefGoogle Scholar
6.Chisholm, M.F., Kumar, S., Hazzledine, P.Dislocations in complex materials. Science 307, 701 (2005)CrossRefGoogle ScholarPubMed
7.Allen, C.W., Liao, K.C.Dislocation models for shear transformations. Phys. Status Solidi A 74, 673 (1982)CrossRefGoogle Scholar
8.Allen, C.W., Liao, K.C.Shear transformations in the Laves phase TiCr2Proceeding of the ICOMAT (Boston, MA 1979) 124Google Scholar
9.Kitano, Y., Komura, Y., Kajiwara, H., Watanabe, E.Two-dimensional lattice images of the Mg-base Friauf-Laves phase and a new type of defect. Acta Crystallogr., Sect. A 36, 16 (1980)CrossRefGoogle Scholar
10.Frank, F.C., Kasper, J.S.Complex alloy structures regarded as sphere apckings. 1. Definitions and basic principles. Acta Crystallogr. 11, (3)184 (1958)CrossRefGoogle Scholar
11.Frank, F.C., Kasper, J.S.Complex alloy structures regarded as sphere packing. 2. Analysis and classification of representative structures. Acta Crystallogr. 12, (7)483 (1959)CrossRefGoogle Scholar
12.Hägg, G.Some notes on MX2 layer lattices with close-packed X atoms. Ark. Kemi Mineral. Geol. 16B, 1 (1943)Google Scholar
13.Kronberg, M.L.Plastic deformation of single crystals of sapphire: Basal slip and twinning. Acta Metall. 5, 507 (1957)CrossRefGoogle Scholar
14.Hazzledine, P.M., Pirouz, P.Synchroshear transformation in Laves phases. Scr. Metall. Mater. 28, 1277 (1993)CrossRefGoogle Scholar
15.Waitz, T., Karnthaler, H.P.High-resolution and in situ transmission electron microscopy investigation of the martensitic fcc-dhcp phase transformations in Co–Fe single crystals. Philos. Mag. A 73, (2)365 (1996)CrossRefGoogle Scholar
16.Heinrich, H., Karnthaler, H.P., Waitz, T., Kostorz, G.Transformation dislocations in Co–Fe. Mater. Sci. Eng., A 272, 238 (1999)CrossRefGoogle Scholar
17.Aufrecht, J., Leineweber, A., Mittemeijer, E.J.Metastable hexagonal modifications of the NbCr2 Laves phase as function of cooling rateAdvanced Intermetallic-Based Alloys for Extreme Environment and Energy Applications edited by M. Palm, B.P. Bewlay, M. Takeyama, J.M.K. Wiezorek, and Y-H. He(Mater. Res. Soc. Symp. Proc. 1128, Warrendale, PA 2009)1128-U08-07481Google Scholar
18.Aufrecht, J., Leineweber, A., Senyshyn, A., Mittemeijer, E.J.The absence of a stable hexagonal Laves phase modification (NbCr2) in the Nb–Cr system. Scr. Mater. 62, (5)227 (2010)CrossRefGoogle Scholar
19.Venkatraman, M., Neumann, J.P.The Cr–Hf (chromium-hafnium) system. Bull. Alloy Phase Diag. 7, (6)570 (1986)CrossRefGoogle Scholar
20.Aufrecht, J., Baumann, W., Leineweber, A., Duppel, V., Mittemeijer, E.J.Layer-stacking irregularities in C36-type Nb–Cr and Ti–Cr Laves phases and their relation with polytypic phase transformations. Philos. Mag. 90, 3149 (2010)CrossRefGoogle Scholar