Internal Stresses and Dislocation Mobility in NaCl Single Crystals

AbstractDislocation velocities have been measured in both lightly and heavily HCl-doped ice single crystals using synchrotron-based, monochromatic X-ray topography. In the temperature range −10°C to −30°C, a concentration of ˜1 × 10−6M was found not to affect the mobility of either 60° or screw basal dislocations, confirming the earlier observations of C. Shearwood and R. W. Whitworth [Philosophical Magazine A65, 1992, 85]. However, heavier doping (˜1.9 × 10−4M) increased the basal dislocation velocity, compared to pure ice, by a factor of 2.6 at −16.4°C.

Download Full-text

Relationship Between Stress and Surface Roughness in Krypton Implanted MgO

MRS Proceedings ◽

10.1557/proc-356-57 ◽

1994 ◽

Vol 356 ◽

Author(s):

Laurence Gea ◽

Jean-Luc Loubet ◽

Roger Brenier ◽

Paul Thevenard

Keyword(s):

Surface Roughness ◽

Atomic Force Microscope ◽

Single Crystals ◽

Internal Stresses ◽

Post Irradiation ◽

Implantation Damage ◽

Atomic Force ◽

Microindentation Technique ◽

Good Agreement

Abstract(001) MgO single crystals were implanted with 150 keV krypton ions (Kr+) at a fluence of 5.1016 ions.cm-2 . The implanted surface, observed with an Atomic Force Microscope (AFM) exhibits striking features that can be described as undulations with a wavelength of 0.5 [μm. We correlate these features to the decrease in density and the stresses induced by the implantation damage. As a matter of fact, a model of surface instabilities provides a relationship between the wavelength of the ondulations and internal stresses. Using this model, implantation stresses are calculated to 2.2 GPa. This is in good agreement with the value of 2 GPa obtained with the help of the microindentation technique and the literature data. Some effects of an ionizing post-irradiation on stress and surface roughness are described.

Download Full-text

Dislocation Mobility and Yield Stress in Silver and Silver-Tin Dilute Alloy Single Crystals

Japanese Journal of Applied Physics ◽

10.1143/jjap.12.751 ◽

1973 ◽

Vol 12 (5) ◽

pp. 751-752 ◽

Cited By ~ 5

Author(s):

Hisaaki Suga ◽

Toru Imura

Keyword(s):

Single Crystals ◽

Yield Stress ◽

Dislocation Mobility ◽

Dilute Alloy

Download Full-text

Influence of Dislocation Mobility on Room and High Temperature Ductility of -Oriented Nial Single Crystals

MRS Proceedings ◽

10.1557/proc-364-413 ◽

1994 ◽

Vol 364 ◽

Cited By ~ 1

Author(s):

M. A. Morris ◽

J. P. Perez ◽

R. Darolia

Keyword(s):

High Temperature ◽

Single Crystals ◽

Room Temperature ◽

Tensile Tests ◽

Slip Systems ◽

Dislocation Mobility ◽

Screw Dislocations ◽

Large Density ◽

Thin Foils

AbstractThe dislocation configurations produced by room and high temperature compression of <100> oriented single crystals of binary NiAl and in those containing iron and hafnium additions have been analysed and compared to those obtained by hardness indentation and TEM insitu tensile tests. Kinking occurs during room temperature compression such that <100> dislocations are activated in all cases but the iron-containing alloy also exhibited a large density of <111> screw dislocations. The latter however, appear immobile when they are created by hardness indentations of thin foils, while only pile-ups of <100> segments can propagate. Similarly, although different slip systems are present after high temperature compression, only <100> dislocation segments have been confirmed to be mobile after room temperature hardness indentation of these predeformed thin foils. The improvement in ductility observed at room temperature in the predeformed specimens of the binary and the iron containing alloys has been attributed to the increased production of these mobile <100> dislocations.

Download Full-text