Diffusion processes in the dislocation cores during the high-temperature deformation of intermetallic alloys.

• Autorzy: Messerschmidt U. , Guder S. , Häussler D. , Bartsch M.

Warianty tytułu

PL

Procesy dyfuzyjne w rdzeniach dyslokacji w trakcie odkształcania wysokotemperaturowego stopów międzymetalicznych.

• Konferencja: XVIth Physical Metallurgy and Materials Science Conference on Advanced Materials and Technologies AMT'2001, Gdańsk-Jurata, 16-20 September, 2001
• Języki publikacji: PL

Abstrakty

EN

In situ straining experiments in a high-voltage electron microscope to study dislocation dynamics and macroscopic deformation experiments including stress relaxation tests have been performed on a number of intermetallic alloys. There are many similarities in the dynamic behaviour of dislocations in the studied materials. In the low-temperature range, different mechanisms lead to a normal decrease of the flow stress with increasing temperature. At high temperatures, in several materials the dislocations move either in an unstable or a viscous way. They are then smoothly curved, or they are straight and oriented along crystallographic directions. As the low-temperature mechanisms cease at high temperatures, the viscous motion should be due to an additional friction mechanism which also causes the flow stress anomaly in the respective materials. It is suggested here that this mechanism involves diffusion processes in the dislocation cores, which can be described by the theory of the Cottrell effect. The diffusing species can be quite different, alloying components or intrinsic point defects like vacancies and antisite defects existing in the lattice or only in the dislocation cores. If the dislocations are straight and crystallographically oriented during their motion, they may be dissociated and move by a succession of glide and conservative climb between the partial dislocations. All these processes lead to an inverse dependence of the strain rate sensivity on the stress.

Słowa kluczowe

PL

dyslokacja; dynamika dyslokacji; odkształcenie; relaksacja naprężeń; stop międzymetaliczny; dyfuzja; temperatura wysoka

EN

dislocation; dislocation dynamics; deformation; stress relaxation; intermetallic alloys; diffusion; high temperature; dislocation core

• Wydawca: Wydawnictwo SIGMA-NOT
• Czasopismo: Inżynieria Materiałowa
• Rocznik: 2001
• Tom: R. XXII, nr 5
• Strony: 627--632
• Opis fizyczny: Bibliogr. 23 poz., tab., rys.

Twórcy

autor

Messerschmidt U.

• Max Planck Institute of Microstructure Physics, Halle/Saale, Germany

autor

Guder S.

• Max Planck Institute of Microstructure Physics, Halle/Saale, Germany

autor

Häussler D.

• Max Planck Institute of Microstructure Physics, Halle/Saale, Germany

autor

Bartsch M.

• Max Planck Institute of Microstructure Physics, Halle/Saale, Germany

• Max Planck Institute of Microstructure Physics, Halle/Saale, Germany

Bibliografia

• [1] U. Messerschmidt, M. Bartsch: High-temperature straining stage for in situ experiments in the high voltage electron microscope. Ultramicroscopy 56 (1994) 163-171.
• [2] U. Messerschmidt. S. Guder, D. Häussler, M. Bartsch, Dislocation dynamics in intermetallic alloys and their macroscopic deformation behaviour, Int. Conf. on Processing and Manufacturing of Advanced Materials, THERMEC 2000, Las Vegas, 4.-8.12.2000. to be published in J. Mater. Proc. Technol.
• [3] U. Messerschmidt, R. Haushälter, M. Bartsch: Microprocesses of the deformation of Ni Al single crystals. Mater. Sci. Eng. A 234-236 ( 1997) 822- 825.
• [4] B. Viguier, K.J. Hemker, J. Bonneville. F. Louchet, J.-L. Martin: Modelling of the flow stress anomaly in-TiAl I. Experimental observations of dislocation mechanisms. Phil. Mag A 71 (1995) 1295-13 12.
• [5] F. Louchet, B. Viguier: Modelling of the flow stress anomaly in γ-TiAI. II. The local pinning-unzipping model: statistical analysis and consequences. Phil. Mag. A 71 (1995) 1313-1333.
• [6] S. Sriram, D.M. Dimiduk, P.M. Hazzledine, V.K. Vasudevan: The geometry and nature os pinning points of 1/2<110] unit dislocations in binary Ti Al alloys. Phil. Mag. A 76 (1997) 965-993.
• [7] U. Messerschmidt, D. Häussler, M. Bansch, G. Sauthoff: Dislocation processes during the deformation of NiAl-0.2at%Ta. Intermetallics 7 (1999) 455-466.
• [8] D. Häussler, M. Bartsch, M. Aindow, l.P. Jones, U. Messerschmidt: Dislocation processes during the plastic deformation of γ Ti Al. Phil. Mag. A 79 (1999) 1045-1071.
• [9] S. Zghal, A. Menand, A. Couret: Pinning points anchoring ordinary and Shockley dislocations in TiAl alloys. Acta mater. 46 (1998) 5899-5905.
• [10] U. Messerschmidt, S. Guder, L. Junker, M, Bartsch, M. Yamaguchi: Microprocesses of the deformntion of single and polycrystalline MoSi2. to be publ. in Mater. Sci. Eng. A
• [11] U. Messerschmidt, S. Guder, D. Häussler, and M. Bartsch, Dislocation dynamics in intermetallic and oxide dispersion strengthened (ODS) alloys. Submitted to MRS Proc., Symp. Y, 2000 Fall Meeting.
• [12] R. Srinivasan, M.F. Savage, R.D. Noebe, M.J. Mills: Effects of deviation from stoichiometry on deformation behavior of hard-oriented Ni Al single crystals. MRS Proc. 552 (1999) KK9.I0.l-6.
• [13] S. Guder, M. Bartsch, M. Yamaguchi, and U. Messerschmidt, Mater. Sci. Eng. A 261 (1999) 138.
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• [15] U. Messerschmidt, M. Bartsch. S., Guder., D. Häßler R., Haushälter, M. Yamaguchi: Dislocation dynamics during the deformation of intermetallic alloys and the flow stress anomaly. MRS Proc. 552 (1999) KK10.9.1-6
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• [17] F. Appel, U. Sparka, J. Müllauer: Work-harening characteristic and recovery os gamma base titanium alurninides MRS Proc 552 (1999) KKJ .7.1-6.
• [18] R. Schroll and P. Gumbsch:Atomistic study of the interaction between dislocations and structural point defects in NiAl. Phys. Status Solidi A 166 (1998) 475 . f
• [19] U. Christoph, F. Appel and R. Wagner: Static and dynamic strain ageing in two-phase γ-titanium aluminides. MRS Proc 460 (1997) 207
• [20] M.J. Mills, R. Srinivasan, M.S. Daw: Observations and modelling of α(011) dislocations in NiAl at intermediate temperatures. Phil Mag A 77 (1998) 801-823.
• [21] R. Srinivasan. M.S. Daw. R O Noebe:. M.J Mills, Observations of glide and decomposition of α(01 1) dislocations al high temperatures in Ni ,44Al single crystals deformed along the hard orientation, submitted to Phil Mag A
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• [23] S. Guder. M. Bansch and U. Messerschmtdt. TEM analysis of planar faults on (001) planes in MoSi2 single crystals, submitted to Phti. Mag A