Electrolytic Isolation of Twin-Type Shock Deformation Structures

1967 ◽  
Vol 25 ◽  
pp. 318-319
Author(s):  
F. I. Grace ◽  
L. E. Murr
Keyword(s):  
Grain Boundaries ◽  
Thin Foil ◽  
Electrolyte Composition ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electron Transmission ◽  
Deformation Structures ◽  
The Matrix ◽  
Average Current ◽  
Specimen Edge

During the course of electron transmission investigations of the deformation structures associated with shock-loaded thin foil specimens of 70/30 brass, it was observed that in a number of instances preferential etching occurred along grain boundaries; and that the degree of etching appeared to depend upon the various experimental conditions prevailing during electropolishing. These included the electrolyte composition, the average current density, and the temperature in the vicinity of the specimen. In the specific case of 70/30 brass shock-loaded at pressures in the range 200-400 kilobars, the predominant mode of deformation was observed to be twin-type faults which in several cases exhibited preferential etching similar to that observed along grain boundaries. A novel feature of this particular phenomenon was that in certain cases, especially for twins located in the vicinity of the specimen edge, the etching or preferential electropolishing literally isolated these structures from the matrix.

Effect of Ultrasonic Electroforming Process Parameters on Reflective Performance of Nickel Casting Layer

2014 ◽  
Vol 488-489 ◽  
pp. 222-227
Author(s):  
Fei Ye ◽  
Guang Yang ◽  
Jun Pi ◽  
Zi Qian Chen
Keyword(s):  
Surface Roughness ◽  
Process Parameters ◽  
Current Density ◽  
Laser Scanning ◽  
Laser Scanning Microscopy ◽  
Ultrasonic Power ◽  
Experimental Conditions ◽  
Average Current Density ◽  
Electroforming Process ◽  
Average Current

In order to improve the reflection coefficient of nickel electroforming layer with microprism structure effectively, controlling electroforming process strictly and adjusting different process parameters are needed for achieve the best electroforming effect. Nickel casting layer was prepared by ultrasonic direct current electroforming on the microprism nickel plate. Surface reflective coefficient of nickel casting layer was measured by retroreflectometer, and the morphology was observed by 3D laser scanning microscopy system. The effects of ultrasonic power, frequency and average current density on the surface reflective performance were studied, experimental results were verified by measuring microprism side surface roughness. The results show that reflective coefficient of nickel casting layer prepared by high frequency ultrasonic electroforming was greater than that by low frequency with other experimental conditions remaining unchanged. It was increased first and then decreased with ultrasonic power and average current density increasing gradually, and the surface roughness measurement also verified this conclusion.

Effect of Frequency on Composition and Microstructure of Siliconized Layer Using Pulse Electrodeposition

2011 ◽  
Vol 189-193 ◽  
pp. 1113-1116 ◽  
Author(s):  
Hai Li Yang ◽  
Ping Ju Hao ◽  
Guo Zhang Tang ◽  
Yun Gang Li
Keyword(s):  
Pulse Current ◽  
Steel Substrate ◽  
Pulse Frequency ◽  
Grain Structure ◽  
Experimental Conditions ◽  
Average Current Density ◽  
High Frequencies ◽  
Fine Grain ◽  
Average Current ◽  
Si Content

The siliconized layer on low silicon steel substrate was produced under pulse current conditions from KCl-NaCl-NaF-SiO2molten salt and the effects of frequency on the composition and microstructure were investigated. The results showed that at the same average current density and other experimental conditions, Si content in the surface and the layer thickness decreased with increasing frequency. Low pulse frequency (500 Hz) and high frequencies (1500, 2000Hz) produced coarse grain and bigger surface roughness. There was a flat fine grain structure and a relatively thick (30m) layer when the frequency was 1000Hz. However, the effect of pulse frequency on the structure of the layer was not obvious. The phase structure of the layer was composed of Fe3Si with (110) preferred orientation at all experimental frequencies.

Optimizing conditions for x-ray microchemical analysis in analytical electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 548-549 ◽  
Author(s):  
N. J. Zaluzec
Keyword(s):  
Solid Angle ◽  
Analytical Electron Microscopy ◽  
Incident Beam ◽  
Thin Foil ◽  
Experimental Conditions ◽  
X Ray ◽  
Microchemical Analysis ◽  
Analytical Electron ◽  
Image Position ◽  
Incident Beam Energy

The ultimate sensitivity of microchemical analysis using x-ray emission rests in selecting those experimental conditions which will maximize the measured peak-to-background (P/B) ratio. This paper presents the results of calculations aimed at determining the influence of incident beam energy, detector/specimen geometry and specimen composition on the P/B ratio for ideally thin samples (i.e., the effects of scattering and absorption are considered negligible). As such it is assumed that the complications resulting from system peaks, bremsstrahlung fluorescence, electron tails and specimen contamination have been eliminated and that one needs only to consider the physics of the generation/emission process.The number of characteristic x-ray photons (Ip) emitted from a thin foil of thickness dt into the solid angle dΩ is given by the well-known equation

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Diffraction effects from inclined grain boundaries in polycrystalline thin foils

1978 ◽  
Vol 36 (1) ◽  
pp. 420-421
Author(s):  
C.B. Carter ◽  
A.M. Donald ◽  
S.L. Sass
Keyword(s):  
Thin Film ◽  
Grain Boundaries ◽  
Boundary Plane ◽  
Foil Surface ◽  
Thin Foils ◽  
The Matrix ◽  
Firm Basis ◽  
Diffraction Patterns ◽  
Wave Matching ◽  
Diffraction Effects

Using thin-film gold bicrystals with the boundary plane parallel to the foil surface, it has been shown(l,2) that networks of grain boundary dislocations can act as diffraction gratings and give rise to subsidiary reflections close to the matrix reflections in electron diffraction patterns. Recently several groups of workers(3-5) have shown that inclined boundaries in polycrystalline specimens also produce extra reflections which may be due to the periodic nature of the boundaries. In general grain boundaries in polycrystalline specimens will be steeply inclined to the foil surface and additional reflections due to wave matching at the boundary(6) will also be present. The diffraction technique has the potential for providing detailed information on the structure of inclined boundaries (see, for example (5)), especially for the case where the image contains no useful information. In order to provide a firm basis for this technique, the geometry of the diffraction effects expected from inclined boundaries and the influence of these effects on the appearance of images will be examined.

Lattice imaging of precipitates in Al-Zn-Mg alloy

1986 ◽  
Vol 44 ◽  
pp. 412-413
Author(s):  
C. K. Wu
Keyword(s):  
Grain Boundaries ◽  
Homogeneous Nucleation ◽  
Alloy System ◽  
Mg Alloy ◽  
List Type ◽  
Lattice Structures ◽  
Type Number ◽  
Orientation Relationships ◽  
Lattice Imaging ◽  
The Matrix

The precipitation phenomenon in Al-Zn-Mg alloy is quite interesting and complicated and can be described in the following categories:(i) heterogeneous nucleation at grain boundaries;(ii) precipitate-free-zones (PFZ) adjacent to the grain boundaries;(iii) homogeneous nucleation of snherical G.P. zones, n' and n phases inside the grains. The spherical G.P. zones are coherent with the matrix, whereas the n' and n phases are incoherent. It is noticed that n' and n phases exhibit plate-like morpholoay with several orientation relationship with the matrix. The high resolution lattice imaging techninue of TEM is then applied to study precipitates in this alloy system. It reveals the characteristics of lattice structures of each phase and the orientation relationships with the matrix.

scholarly journals Application of the Composite Hardness Models in the Analysis of Mechanical Characteristics of Electrolytically Deposited Copper Coatings: The Effect of the Type of Substrate

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 111
Author(s):  
Ivana O. Mladenović ◽  
Nebojša D. Nikolić ◽  
Jelena S. Lamovec ◽  
Dana Vasiljević-Radović ◽  
Vesna Radojević
Keyword(s):  
Mechanical Characteristics ◽  
Dislocation Creep ◽  
Average Current Density ◽  
Fine Grained ◽  
Copper Coatings ◽  
Electrochemically Deposited ◽  
Composite Models ◽  
Average Current ◽  
Composite Hardness ◽  
Coating Hardness

The mechanical characteristics of electrochemically deposited copper coatings have been examined by application of two hardness composite models: the Chicot-Lesage (C-L) and the Cheng-Gao (C-G) models. The 10, 20, 40 and 60 µm thick fine-grained Cu coatings were electrodeposited on the brass by the regime of pulsating current (PC) at an average current density of 50 mA cm−2, and were characterized by scanning electron (SEM), atomic force (AFM) and optical (OM) microscopes. By application of the C-L model we determined a limiting relative indentation depth (RID) value that separates the area of the coating hardness from that with a strong effect of the substrate on the measured composite hardness. The coating hardness values in the 0.9418–1.1399 GPa range, obtained by the C-G model, confirmed the assumption that the Cu coatings on the brass belongs to the “soft film on hard substrate” composite hardness system. The obtained stress exponents in the 4.35–7.69 range at an applied load of 0.49 N indicated that the dominant creep mechanism is the dislocation creep and the dislocation climb. The obtained mechanical characteristics were compared with those recently obtained on the Si(111) substrate, and the effects of substrate characteristics such as hardness and roughness on the mechanical characteristics of the electrodeposited Cu coatings were discussed and explained.

MICROSTRUCTURAL EVOLUTION OF Al-Cu-Mg-Ag ALLOY WITH TRACE Zr ADDITION DURING TWO-STEP HOMOGENIZATION

2009 ◽  
Vol 23 (06n07) ◽  
pp. 855-862 ◽  
Author(s):  
FEIYUE MA ◽  
ZHIYI LIU
Keyword(s):  
Melting Point ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Cast Alloy ◽  
Scanning Calorimetry ◽  
Zr Addition ◽  
Homogenization Time ◽  
The Matrix ◽  
Higher Temperature ◽  
Lower Temperature

The microstructural evolution in an Al - Cu - Mg - Ag alloy with trace Zr addition during homogenization treatment was characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDS). It was shown that the low-melting-point phase segregating toward grain boundaries is Al 2 Cu , with a melting point of 523.52°C. A two-step homogenization process was employed to optimize the microstructure of the as-cast alloy, during which the alloy was first homogenized at a lower temperature, then at a higher temperature. After homogenized at 420°C for 6 h, Al 3 Zr particles were finely formed in the matrix. After that, when the alloy was homogenized at an elevated temperature for a longer time, i.e., 515°C for 24 h, most of the precipates at the grain boundaries were removed. Furthermore, the dispersive Al 3 Zr precipitates were retained, without coarsening greatly in the final homogenization step. A kinetics model is employed to predict the optimal homogenization time at a given temperature theoretically, and it confirms the result in present study, which is 420°C/6h+515°C/24h.

Microstructure of Polycrystalline MgO Penetrated by a Silicate Liquid

1996 ◽  
Vol 2 (3) ◽  
pp. 113-128 ◽  
Author(s):  
Sundar Ramamurthy ◽  
Michael P. Mallamaci ◽  
Catherine M. Zimmerman ◽  
C. Barry Carter ◽  
Peter R. Duncombe ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Glassy Phase ◽  
Silicate Liquid ◽  
Two Phase ◽  
The Matrix ◽  
Devitrification Process ◽  
Phase Mixture

Dense, polycrystalline MgO was infiltrated with monticellite (CaMgSiO4) liquid to study the penetration of liquid along the grain boundaries of MgO. Grain growth was found to be restricted with increasing amounts of liquid. The inter-granular regions were generally found to be comprised of a two-phase mixture: crystalline monticellite and a glassy phase rich in the impurities present in the starting MgO material. MgO grains act as seeding agents for the crystallization of monticellite. The location and composition of the glassy phase with respect to the MgO grains emphasizes the role of intergranular liquid during the devitrification process in “snowplowing” impurities present in the matrix.

The efficient use of stabilizing materials in superconducting solenoids

1969 ◽  
Vol 47 (13) ◽  
pp. 1401-1407 ◽  
Author(s):  
Richard Stevenson
Keyword(s):  
Current Density ◽  
Transient Heat Conduction ◽  
Point Of View ◽  
Average Current Density ◽  
Initial Current ◽  
Current Sharing ◽  
Purity Aluminium ◽  
High Purity Aluminium ◽  
Average Current ◽  
Composite Conductor

The problem of stability of superconducting solenoids is considered from a thermal point of view. The transient heat conduction equation for a superconducting tape clad with normal material and operated in a current sharing mode is studied, and a solution for the temperature distribution is obtained. The composite conductor is considered stable if its final temperature in the current sharing mode corresponds to the critical temperature for the initial current density in the superconductor. Using this criterion, the operating point of the superconductor and its stabilizing cladding thickness can be chosen to give a maximum average current density in the composite conductor at any field. Calculations are given for Nb3Sn tape clad with OFHC copper and with high purity aluminium.

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