Mechanism of kink band formation in zinc single crystals

Author(s):  
Krzysztof Pieła ◽  
Andrzej Korbel

Abstract This paper is focused on the mechanism of kink band formation. In the general case, lattice rotation in a kink band may be realized by two sequentially activated simple elastic shears in nearly perpendicular planes. In the case of zinc crystals, compressed along (0001) plane at the temperature 523 K, the first shear may result from stress-induced temporary lattice instability (movement of atoms towards metastable positions in tetrahedric holes), while the second shear occurring along a temporary ‘new-positioned’ basal plane immediately ‘rebuilds’ the stable lattice.

2007 ◽  
Vol 48 (4) ◽  
pp. 759-763 ◽  
Author(s):  
Tatsuya Okada ◽  
Hiroyuki Y. Yasuda ◽  
Tetsuya Watanabe ◽  
Fukuji Inoko ◽  
Yukichi Umakoshi

2007 ◽  
Vol 280-283 ◽  
pp. 1343-1346 ◽  
Author(s):  
Shi Bo Li ◽  
Hong Xiang Zhai

Microscale plasticity of Ti3SiC2 was investigated by Vickers hardness indentation. The surface layer of the hardness indentations was removed by acid solution to observe microstructure beneath the indentations, where a large number of bending, delamination and kinking grains were found. These features suggest that Ti3SiC2 is able to consume microdamage around the indentations. Numerous basal plane dislocations and stacking faults lying in Ti3SiC2 grains or accumulating at grain boundaries were observed. The basal plane dislocations play an important role in the microscale plastic deformation. The plasticity and damage tolerance for Ti3SiC2 at room temperature should be attributed to multiple energy absorbing mechanisms: grains bending, delamination, kink-band formation, and the basal plane slip, etc.


2019 ◽  
Vol 806 ◽  
pp. 1384-1393 ◽  
Author(s):  
Kosuke Takagi ◽  
Tsuyoshi Mayama ◽  
Yoji Mine ◽  
Yu Lung Chiu ◽  
Kazuki Takashima

Author(s):  
Y. Feng ◽  
X. Y. Cai ◽  
R. J. Kelley ◽  
D. C. Larbalestier

The issue of strong flux pinning is crucial to the further development of high critical current density Bi-Sr-Ca-Cu-O (BSCCO) superconductors in conductor-like applications, yet the pinning mechanisms are still much debated. Anomalous peaks in the M-H (magnetization vs. magnetic field) loops are commonly observed in Bi2Sr2CaCu2Oy (Bi-2212) single crystals. Oxygen vacancies may be effective flux pinning centers in BSCCO, as has been found in YBCO. However, it has also been proposed that basal-plane dislocation networks also act as effective pinning centers. Yang et al. proposed that the characteristic scale of the basal-plane dislocation networksmay strongly depend on oxygen content and the anomalous peak in the M-H loop at ˜20-30K may be due tothe flux pinning of decoupled two-dimensional pancake vortices by the dislocation networks. In light of this, we have performed an insitu observation on the dislocation networks precisely at the same region before and after annealing in air, vacuumand oxygen, in order to verify whether the dislocation networks change with varying oxygen content Inall cases, we have not found any noticeable changes in dislocation structure, regardless of the drastic changes in Tc and the anomalous magnetization. Therefore, it does not appear that the anomalous peak in the M-H loops is controlled by the basal-plane dislocation networks.


2018 ◽  
Vol 149 ◽  
pp. 66-73 ◽  
Author(s):  
Vedad Tojaga ◽  
Simon P.H. Skovsgaard ◽  
Henrik Myhre Jensen

1999 ◽  
Author(s):  
Kenji Oguni ◽  
G. Ravichandran

Abstract Results from an experimental investigation on the mechanical behavior of a unidirectional reinforced polymer composite with 50% volume fraction E-glass/vinylester under uniaxial and proportional multiaxial compression are presented. Specimens are loaded in the fiber direction using a servo-hydraulic material testing system for low strain rates and a Kolsky (split Hopkinson) pressure bar for high strain rates, up to 3000 s−1. The results indicate that the compressive strength of the composite increases with increasing levels of confinement and increasing strain rates. Post-test optical and scanning electron microscopy is used to identify the failure modes. The failure mode that is observed in unconfined specimen is axial splitting followed by fiber kink band formation. At high levels of confinement, the failure mode transitions from axial splitting to kink band formation and fiber failure. Also, a new energy based analytic model for studying axial splitting phenomenon in unidirectional fiber-reinforced composites is presented.


A summary is given of some present ideas on the mechanism of work-hardening of single crystals and polycrystalline materials. In particular, the difference is stressed between the three stages of hardening: stage I, or easy glide; stage II, the region of rapid hardening accompanied by short slip lines; and stage III, the region of slow or parabolic hardening which is temperature-dependent and in which long slip bands are formed.


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