Sub-Grain Size and Hall-Petch Relation in Pure Copper Single Crystals

2007 ◽  
Vol 345-346 ◽  
pp. 29-32
Author(s):  
Sei Miura ◽  
Yoshito Nishimura ◽  
Nagato Ono
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Single Crystals ◽  
Pure Copper ◽  
Petch Relation ◽  
Low Dislocation Density ◽  
Initial Dislocation Density ◽  
Bridgeman Method ◽  
Copper Single Crystals ◽  
Critical Resolved Shear Stress

The effect of sub-grain on the yield stress of pure copper single crystals with the [253] orientation was investigated by using the etch pit technique. The single crystal plates were successfully prepared from the seed crystals, which were produced at the melting temperature of 1473 K by the Bridgeman method. The present investigation confirmed the Hall-Petch relation concerning the effect of sub-grain boundaries on the macroscopic yielding of pure copper. The result derived from the extrapolation of the relationship of critical resolved shear stress (CRSS) and the initial dislocation density and sub-grain size is in good agreement with the evaluation in high purity copper single crystals of low dislocation density.

scholarly journals Assessment of Internal Stresses Using Dislocation Dipole Heights in Cyclically Deformed [001] Copper Single Crystals

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 512 ◽  
Author(s):  
Roya Ermagan ◽  
Maxime Sauzay ◽  
Michael Ernest Kassner
Keyword(s):  
Dislocation Density ◽  
Single Crystals ◽  
Long Range ◽  
Applied Stress ◽  
Internal Stresses ◽  
Single Slip ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Local Stresses ◽  
Copper Single Crystals

There have been a number of studies on dipole separations in cyclically deformed FCC single crystals in single slip while there are no such studies in multiple slip. The dipole heights provide insight into the presence of long-range internal stresses (LRIS). In this study, we investigated how LRIS compare with the single slip studies through measuring the dislocation of dipole heights. [001] oriented copper single crystals were cyclically deformed in strain-control to saturation at ambient temperature. Transmission electron microscopy (TEM) confirms a labyrinth dislocation microstructure with high dislocation density walls and low dislocation density channels. The maximum dipole heights under the saturation stress were approximately independent of location, being nearly equal in the walls and within the channels. This, by itself, supports a uniform stress across the microstructure and low long-range internal stresses. The maximum value for dipole heights suggests dipole strengths (local stresses) that are about a factor of 2.4 higher than the applied stress based on the usual athermal equations. Considering the small “extra” stress that may be provided by tripoles or small dislocation pile-ups, a nearly homogenous stress distribution with only small internal stresses may be present, which is consistent with the observation of uniform dipole height across the heterogeneous dislocation microstructure. This observation that the stress state appears to be homogenous and higher than the applied stress has also been reported in the case of cyclically deformed metals in single slip.

Size Effects in LiF Micron-Scale Single Crystals of Low Dislocation Density

2006 ◽  
Vol 976 ◽  
Author(s):  
Edward M. Nadgorny ◽  
Dennis M. Dimiduk ◽  
Michael D. Uchic
Keyword(s):  
Flow Stress ◽  
Dislocation Density ◽  
Single Crystals ◽  
Size Effects ◽  
Bulk Crystals ◽  
Stochastic Variation ◽  
Deformation Response ◽  
Low Dislocation Density ◽  
Initial Dislocation Density ◽  
Micron Diameter

AbstractThis study examines the deformation response of 20, 5, and 1 micron diameter samples fabricated by FIB-milling from bulk ultrapure LiF single crystals. The bulk crystals have a very low initial dislocation density as revealed by an etch-pit technique. Two types of <001> microsamples were deformed preferentially by single slip when compressed inside a nanoindentation system. Similar to previously studied FCC-derivative metals, LiF microsamples demonstrate dramatic strengthening achieving the engineering flow stress σ ≈ 650 MPa in 1-μm samples. The stress-diameter dependence obeys a power law, σ ∼ D−m, where m ≈ 0.8. Stochastic variation of flow stress, fast intermittent deformation events (“avalanches”) and highly localized slip bands after avalanches - all characteristic of size effects in metals, are also observed in LiF. Possible dislocation mechanisms of the observed size effects are discussed.

Growth Of Low-Dislocation-Density InP Single Crystals By The VCZ Method

1989 ◽  
Author(s):  
M. Tatsumi ◽  
T. Kawase ◽  
T. Araki ◽  
N. Yamabayashi ◽  
T. Iwasaki ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Single Crystals ◽  
Low Dislocation Density

Topographic study of dislocation structure in hexagonal SiC single crystals with low dislocation density

2007 ◽  
Vol 304 (1) ◽  
pp. 57-63 ◽  
Author(s):  
Daisuke Nakamura ◽  
Satoshi Yamaguchi ◽  
Itaru Gunjishima ◽  
Yoshiharu Hirose ◽  
Tsunenobu Kimoto
Keyword(s):  
Dislocation Density ◽  
Single Crystals ◽  
Dislocation Structure ◽  
Low Dislocation Density

Growth of GaN single crystals with extremely low dislocation density by two-step dislocation reduction

2009 ◽  
Vol 311 (10) ◽  
pp. 3019-3024 ◽  
Author(s):  
Fumio Kawamura ◽  
Masaki Tanpo ◽  
Naoya Miyoshi ◽  
Mamoru Imade ◽  
Masashi Yoshimura ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Single Crystals ◽  
Low Dislocation Density ◽  
Dislocation Reduction
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