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 MSCE  Vol.4 No.4 , April 2016
I Ions as Obstacles to Dislocation Motion in NaCl:I Single Crystals
Abstract: Strain-rate cycling tests associated with the ultrasonic oscillation were conducted for the purpose of investigation on the interaction between dislocation and I ions during plastic deformation of NaCl:I (0.5 mol% in the melt) at 77 K to room temperature. The relative curves of stress decrement (Δt) due to the oscillation and strain-rate sensitivity ( ) have stair-like shape for NaCl single crystals doped with I at low temperatures. There are two bending points and two plateau regions. λ decreases with Δt between the two bending points. τp at Δt of first bending point and λp between λ at first plateau place and at second one depend on the dopant ions as weak obstacles to dislocation motion. Not only temperature dependence of τp and λp but also τp versus V (activation volume) reflects the interaction between dislocation and I ions. On the basis of the data (i.e. τp and λp) analyzed in terms of the relative curves of Δt and λ, the activation energy, G0, for the overcoming of dislocation from the dopant ion is found to be 0.47 and 0.53 eV for NaCl:Br and NaCl:I, respectively. This result that G0 for NaCl:I is somewhat larger than for NaCl:Br leads to the phenomenon that I ions are slightly stronger than Br ones as weak obstacles to dislocation motion because of the difference between isotropic strains around I ion and around Br in NaCl single crystal. Furthermore, the values of τp0 and Tc are also obtained for the two kinds of specimens. τp0 and Tc are the value of τp at absolute zero and critical temperature at which τp becomes zero.
Cite this paper: Kohzuki, Y. and Ohgaku, T. (2016) I Ions as Obstacles to Dislocation Motion in NaCl:I Single Crystals. Journal of Materials Science and Chemical Engineering, 4, 1-8. doi: 10.4236/msce.2016.44001.
References

[1]   Susyñska, M. (1974) Effect of Impurity Concentration and Plastic Deformation on Dislocation Density of KCl Crystals. Kristall und Technik, 9, 1199-1207.
http://dx.doi.org/10.1002/crat.19740091015

[2]   Kataoka, T. and Yamada, T. (1977) Yield Strength and Dislocation Mobility of KCl-KBr Solid Solution Single Crystals. Japanese Journal of Applied Physics, 16, 1119-1126.
http://dx.doi.org/10.1143/JJAP.16.1119

[3]   Okazaki, K. (1996) Solid-Solution Hardening and Softening in Binary Iron Alloys. Journal of Materials Science, 31, 1087-1099.
http://dx.doi.org/10.1007/BF00352911

[4]   Tabachnikova, E.D., Podolskiy, A.V., Smirnov, S.N., Psaruk, I.A. and Liao, P.K. (2014) Temperature Dependent Mechanical Properties and Thermal Activation Plasticity of Nanocrystalline and Coarse Grained Ni-18.75 at.% Fe Alloy. IOP Conference Series: Materials Science and Engineering, 63, 012105.
http://dx.doi.org/10.1088/1757-899X/63/1/012105

[5]   Messerschmidt, U., Appel, F. and Schmid, H. (1985) The Radius of Curvature of Dislocation Segments in MgO Crystals Stressed in the High-Voltage Electron Microscope. Philosophical Magazine, 51, 781-796.
http://dx.doi.org/10.1080/01418618508237587

[6]   Kataoka, T., Ohji, H., Kishida, K., Azuma, K. and Yamada, T. (1990) Direct Observation of Glide Dislocations in a KCl Crystal by the Light Scattering Method. Applied Physics Letters, 56, 1317-1319.
http://dx.doi.org/10.1063/1.102504

[7]   Ivanov, V.I., Lebedev, A.B., Kardashev, B.K. and Nikanorov, S.P. (1986) Interaction of Dislocations with Pinning Centers in Magnesium at temperatures 295-4.2K. Soviet Physics-Solid State, 28, 867-868.

[8]   Kosugi, T. and Kino, T. (1987) Experimental Determination of the Force-Distance Relation for the Interaction between a Dislocation and a Solute Atom. Journal of the Physical Society of Japan, 56, 999-1009.
http://dx.doi.org/10.1143/JPSJ.56.999

[9]   Kosugi, T. (2001) Temperature Dependence of Amplitude-Dependent Internal Friction Due to Simultaneous Breakaway of a Dislocation from Several Pinning Points. Materials Science and Engineering: A, 309-310, 203-206.
http://dx.doi.org/10.1016/S0921-5093(00)01792-5

[10]   Johnston, W.G. and Gilman, J.J. (1959) Dislocation Velocities, Dislocation Densities, and Plastic Flow in Lithium Fluoride Crystals. Journal of Applied Physics, 30, 129-144.
http://dx.doi.org/10.1063/1.1735121

[11]   Granato, A.V. and Lücke, K. (1956) Theory of Mechanical Damping Due to Dislocations. Journal of Applied Physics, 27, 583-593.
http://dx.doi.org/10.1063/1.1722436

[12]   Blaha, F. and Langenecker, B. (1955) Dehnung von Zink-Kristallen unter Ultraschalleinwirkung. Naturwissenschaften, 42, 556.
http://dx.doi.org/10.1007/BF00623773

[13]   Cottrell, A.H. and Bilby, B.A. (1949) Dislocation Theory of Yielding and Strain Ageing of Iron. Proceedings of the Physical Society of London, A62, 49-62.
http://dx.doi.org/10.1088/0370-1298/62/1/308

[14]   Ohgaku, T. and Teraji, H. (2001) Investigation of Interaction between a Dislocation and a Br–Ion in NaCl:Br– Single Crystals. Physica Status Solidi (a), 187, 407-413.
http://dx.doi.org/10.1002/1521-396X(200110)187:2<407::AID-PSSA407>3.0.CO;2-Q

[15]   Kohzuki, Y. (2010) Bending Angle of Dislocation Pinned by an Obstacle and the Friedel Relation. Philosophical Magazine, 90, 2273-2287.
http://dx.doi.org/10.1080/14786431003636089

[16]   Kohzuki, Y., Ohgaku, T. and Takeuchi, N. (1995) Interaction between a Dislocation and Various Divalent Impurities in KCl Single Crystals. Journal of Materials Science, 30, 101-104.
http://dx.doi.org/10.1007/BF00352137

[17]   Ohgaku, T. and Matsunaga, T. (2009) Interaction between Dislocation and Divalent Impurity in KBr Single Crystals. IOP Conference Series: Materials Science and Engineering, 3, 012021.
http://dx.doi.org/10.1088/1757-899X/3/1/012021

[18]   Friedel, J. (1964) Dislocations. Pergamon Press, Oxford, 223-226.

 
 
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