Laser Irradiation of Nickel: Defect Structures and Surface Alloying

1980 ◽  
Vol 1 ◽  
Author(s):  
L. Buene ◽  
D.C. Jacobson ◽  
S. Nakahara ◽  
J.M. Poate ◽  
C.W. Draper ◽  
...  
Keyword(s):  
Laser Radiation ◽  
Dislocation Density ◽  
Single Crystals ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Dislocation Network ◽  
Defect Structures ◽  
Surface Alloying ◽  
Surface Layers ◽  
Laser Melting

ABSTRACTSurface layers of Ni crystals have been melted with Q-switched Nd-YAG laser radiation. The epitaxially regrown surface layers show significant differences between 〈100〉 and 〈111〉 crystals cut from the same boule. The 〈100〉 crystals exhibit a dislocation cell structure with a dislocation density of l011 - 1012 cm-2. The 〈111〉 crystals contain a laterally uniform dislocation network resulting in a much higher dislocation density for the 〈111〉 surface. The elements Ag, Au, Pd, Sn and Ta have been implanted into Ni single crystals at surface concentrations of up to 20 at %. All the as- implanted systems demonstrate solid solubility. We have used these implanted systems to study the alloys formed by laser melting of Ni. In all systems, with the exception of Ag, 100% of the atoms are trapped on lattice sites.

scholarly journals Effect of Tempering Treatment on Microstructural Evolution and Mechanical Behavior of Heavy-Wall Heat Induction Seamless Bend Pipe

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 259
Author(s):  
Juntai Hu ◽  
Yu Liu ◽  
Ge Wang ◽  
Qiang Li ◽  
Jianyang Wen ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Dislocation Density ◽  
Uniform Elongation ◽  
Cell Structure ◽  
Optical Microscope ◽  
Dislocation Cell ◽  
Granular Bainite ◽  
Tempering Temperature ◽  
Bend Pipe ◽  
Tempering Treatment

In this paper, the microstructure and mechanical properties of heavy-wall seamless bend pipe after quenching at different tempering temperatures, including 550 °C, 600 °C, 650 °C, and 700 °C, were studied. Microstructure and dislocations observations were characterized by means of an optical microscope, a scanning electron microscope, a transmission electron microscope, and X-ray diffraction. As the tempering temperature increases, the dislocation density in the test steel gradually decreases, and the precipitation behavior of (Nb, V)(C, N) increases. The sample tempered at 650 °C exhibits a granular bainite structure with a dislocation cell structure and a large number of smaller precipitates. The yield platforms of tempered samples at 650 °C and 700 °C are attributed to the pinning effect of the Cottrell atmosphere on dislocations. The sample tempered at 650 °C not only presents the highest strength, but also the highest uniform elongation, which is attributed to the higher strain-hardening rate and instantaneous work-hardening index. This is closely related to the multiplication of dislocations, the interaction between dislocations and dislocations, and the interaction between dislocations and precipitates during plastic deformation of the 650 °C-tempered samples with low dislocation density, which delays the occurrence of necking.

X-ray determination of dislocation density and arrangement in plastically deformed copper

2000 ◽  
Vol 33 (5) ◽  
pp. 1284-1294 ◽  
Author(s):  
D. Breuer ◽  
P. Klimanek ◽  
W. Pantleon
Keyword(s):  
Dislocation Density ◽  
Profile Analysis ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Double Crystal ◽  
Mean Values ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
X Ray Scattering

Using the kinematical theory of X-ray scattering by crystals with dislocations as developed by Krivoglazet al.and Wilkens, the dislocation content of compressed copper single and polycrystals was investigated by means of profile analysis of selected diffraction peaks. Measurements of radial intensity distributionsI(2θ) were performed with a double-crystal spectrometer in the case of the single crystals and with conventional polycrystal diffractometers in the case of the polycrystals. Additionally, the misorientations Θ occurring within the dislocation cell structure because of the accumulation of excess dislocations of one sign were investigated by means of rocking curves of the single-crystal reflections and by evaluation of electron backscattering patterns (EBSPs). Within a wide deformation range, the mean total dislocation density ρdcan be related well to the flow stressviathe Taylor relationship. Assuming a random distribution of the misorientations Θ between adjacent dislocation cells, the evaluation of the rocking curves gives mean values 〈|Θ|〉 much smaller than those determined by EBSP analysis. For this reason, a model of a dislocation cell structure with restrictedly correlated misorientations, which leads to better agreement of the X-ray and the EBSP data, is proposed.

Asymmetric X-ray line broadening of plastically deformed crystals. II. Evaluation procedure and application to [001]-Cu crystals

1989 ◽  
Vol 22 (1) ◽  
pp. 26-34 ◽  
Author(s):  
T. Ungár ◽  
I. Groma ◽  
M. Wilkens
Keyword(s):  
Dislocation Density ◽  
Dislocation Structure ◽  
Cell Structure ◽  
Dislocation Cell ◽  
Line Profiles ◽  
Line Broadening ◽  
Spatial Fluctuation ◽  
X Ray ◽  
Dislocation Cell Structure ◽  
Dipole Polarization

In paper I [Groma, Ungár & Wilkens (1988). J. Appl. Cryst. 21, 47–53] a theory was developed to interpret the asymmetric X-ray line broadening of plastically deformed crystals. It was shown that the dislocation structure can be described by five distinct parameters, namely the dislocation density, the mean quadratic spatial fluctuation of the dislocation density, the effective outer cut-off radius, the dipole polarization and the spatial fluctuation of the dipole polarization of the dislocation structure. In this paper a procedure is developed to evaluate these parameters from the Fourier transform of the line profiles. The theory and this procedure are tested by applying it to the asymmetric line profiles of tensile-deformed Cu single crystals orientated for ideal multiple slip. The asymmetry of these profiles is assigned to the dipole polarization of the dislocation cell structure and is directly correlated to residual long-range internal stresses. It is shown that the data can be interpreted in terms of the quasi-composite model of the dislocation cell structure developed earlier for the same material.

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

TEM study on fine carbide precipitates and dislocation cell structure

1990 ◽  
Vol 48 (4) ◽  
pp. 904-905
Author(s):  
Mengzhe Chen ◽  
Siqin Wang ◽  
Jun Ke
Keyword(s):  
Carbide Particle ◽  
Cell Structure ◽  
Ferrite Matrix ◽  
Dislocation Cell ◽  
Isothermal Treatment ◽  
Particle Sizes ◽  
Dislocation Cell Structure ◽  
Thin Foils ◽  
Hsla Steels ◽  
Fine Carbide

A series of investigations have been conducted into the nature and origin of the dislocation cell structure. R.J.Klassen calculated that the dislocation cell limiting size in pure ferrite matrix is about 0.4 μm. M.N.Bassion estimated the size of dislocation cell in deformed ferrite of HSLA steels to be of the same order.In this paper, TEM observation has been concentrated on the interaction of fine carbide precipitates with dislocation cell structure in deformed Fe-C-V (0.05%C, 0.13% and 0.57%V) and Fe-C-Nb (0.07 %C and 0.04%Nb) alloys and compared with that in Fe-C (0.05%). Specimens were austenitized at 1500 “C/20 min and followed by isothermal treatment at 750 °C and 800 “C for 20, 40 and 120 minutes . The carbide particle sizes in these steels are from 9 to 86nm measured from carbon extraction replicas. Specimens for TEM were cut from differently deformed areas of tensile specimens deformed at room temperture. The thin foils were jet electropolished at -20 C in a solution of 10% perchloric acid and 90% ethanol. The TEM observation was carried out in JEM 100CX , EM420 at 100kv and JEM 2000FX at 200kv.

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
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