Internal Friction in Plastically Deformed High-Purity NiAl Single Crystals

1998 ◽  
Vol 552 ◽  
Author(s):  
M. Hirscher ◽  
D. Schaible
Keyword(s):  
Internal Friction ◽  
Single Crystals ◽  
High Purity ◽  
Formation Enthalpy ◽  
Dislocation Motion ◽  
Zone Melting ◽  
Interstitial Impurity ◽  
Impurity Atoms ◽  
Kink Pair ◽  
Friction Measurements

ABSTRACTHigh-purity stoichiometric NiAl single crystals have been prepared by crucible-free inductive zone melting and afterwards well annealed at temperatures below 1200 K. Internal friction measurements of torsionally deformed single crystals show two relaxation maxima at 500 and 800 K which anneal during the measurement. The first maximum can be assigned to the dislocation motion by kinkpair formation and the annealing to pinning of these dislocations by interstitial impurity atoms. The second maximum is attributed to the Snoek-Köster relaxation of dislocations in the presence of mobile interstitial impurity atoms and the annealing to the pinning of dislocations by vacancies. The kink-pair formation enthalpy in NiAl was estimated.

Effect of Purity on Dislocation-Induced Relaxations in Molybdenum Single Crystals

2015 ◽  
Vol 363 ◽  
pp. 106-111
Author(s):  
Shigeru Suzuki ◽  
Alfred Seeger
Keyword(s):  
Internal Friction ◽  
Single Crystals ◽  
High Purity ◽  
Low Frequency ◽  
Activation Process ◽  
Dislocation Interaction ◽  
Dissolved Carbon ◽  
Dislocation Pinning ◽  
Friction Measurements ◽  
Substitutional Impurities

Dislocation-induced relaxations in different molybdenum single crystals were investigated by means of low-frequency internal friction measurements in the temperature range of 20–600 K. The results indicated that the appearance of the dislocation-induced relaxations strongly depends on the purity of the molybdenum, although the intrinsic dislocation relaxations appeared at about 100 K and 450 K in the high-purity molybdenum. The molybdenum containing a small amount of carbon did not exhibit the intrinsic dislocation relaxations but rather revealed a modulus increase due to the dislocation pinning caused by the dissolved carbon. When the molybdenum containing a small amount of carbon was annealed up to 700 K, a new relaxation peak appeared at about 450 K. The activation process for this relaxation indicated that it could be attributed to the relaxation due to a carbon-dislocation interaction. In addition, it was shown that the dislocation-induced relaxations in medium-purity molybdenum were small, which was attributed to the residual substitutional impurities in the molybdenum.

AMPLITUDE-DEPENDENT INTERNAL FRICTION IN HIGH PURITY MOLYBDENUM SINGLE CRYSTALS IN THE TEMPERATURE RANGE 5.9 - 300 K

1981 ◽  
Vol 42 (C5) ◽  
pp. C5-55-C5-60
Author(s):  
H. J. Kaufmann ◽  
P. P. Pal-Val ◽  
D. Schulze ◽  
V. I. Startsev
Keyword(s):  
Internal Friction ◽  
Single Crystals ◽  
High Purity ◽  
Temperature Range

Twofold Resonance in the Internal Friction Measurements of Tin Single Crystals

1973 ◽  
Vol 12 (9) ◽  
pp. 1466-1467
Author(s):  
Toshio Yokoyama ◽  
Gen-ichi Kamoshita ◽  
Hironobu Nishikawa
Keyword(s):  
Internal Friction ◽  
Single Crystals ◽  
Friction Measurements

TEM In-Situ Study of Dislocation Motion in B2 NiAl Single Crystals

1996 ◽  
Vol 460 ◽  
Author(s):  
B. Ghosh ◽  
M. A. Crimp
Keyword(s):  
Single Crystals ◽  
High Purity ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Dislocation Motion ◽  
Thermal Treatments ◽  
Commercially Pure ◽  
Transmission Electron ◽  
Uniform Manner

ABSTRACTIn an effort to understand dislocation mobility in stoichiometric NiAl single crystals, in-situ tensile deformation experiments have been performed in a transmission electron microscope. Commercially pure and high purity single crystals with <001> and <110> orientations have been examined. Two different thermal treatments were adopted in order to effect the mechanical response. Dislocation motion was observed in all samples. Pre-existing dislocations, either isolated or tangled, were not observed to move at any point leading up to sample failure. Cross-slip of the mobile dislocations was observed in some cases. In commercially pure single crystals, dislocations were found to move at a much slower rate and uniform manner in contrast to motion in high purity single crystals which occurs by rapid jumps.

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