The Influence of Quenching Baths on Grain Boundary Wetting Transition in Sn–25 at% In alloy

2008 ◽  
Vol 273-276 ◽  
pp. 649-654
Author(s):  
C.H. Yeh ◽  
L.S. Chang ◽  
Boris B. Straumal
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Liquid Nitrogen ◽  
Liquid State ◽  
Metallographic Analysis ◽  
Wetting Transition ◽  
X Ray Diffraction ◽  
X Ray ◽  
Saturated Water ◽  
Grain Boundary Wetting

The wetting behavior of grain boundaries is affected by temperature, pressure and misorientation of grain boundaries. However, the influence of quenching baths on liquid state grain boundary wetting is rarely reported. In this work, this effect in the Sn−25 at% In alloy was investigated. The Sn−In alloy was prepared by smelting of In and Sn at 300°C for 6 hr in Ar atmosphere. Samples were annealed at temperature between 130 and 165°C and quenched in two kinds of baths: −10°C salt-saturated water and liquid nitrogen. The results from X-ray diffraction show a difference in preferential orientations between samples quenched in these two baths. Metallographic analysis reveals that the percentage of grain boundaries fully wetted in samples quenched in −10°C salt-saturated water is lower than that quenched in liquid nitrogen. It is pointed out that a proper quenching bath is necessary for preserving the initial microstructure of grain boundary wetting.

scholarly journals Structure and Behaviour of Grain Boundaries in Polycrystalline Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 589-605
Author(s):  
Akira Higashi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Moving Boundary ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Geometrical Model ◽  
Grain Boundary Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polycrystalline Ice

AbstractRecent progress in studies of the structure and behaviour of grain boundaries in ice are reviewed. As a lattice geometrical model of the boundary, the coincidence-site lattice (CSL) model is considered for ice crystals. Some evidence of the validity of this model is presented through observations of special shapes of natural snow, results of grain-boundary energy measurements, and direct microscopic observations of boundaries by X-ray diffraction topography. Although methods of measurement of grain-boundary energy have been developed recently, results are still not adequate to be analysed in terms of real energetics for comparison with models of atomic bonding. Modern methods of observing grain boundaries in ice using X-ray diffraction topography are described. Observations of migrating boundaries have revealed that faceting along most closely packed CSL points impede the migration of the CSL boundaries whilst increased numbers of steps among facets with boundaries of other kinds enhance it. The mobility of a fast-moving boundary has been determined to be of the order of 10-10 cm3 dyn-1 s-1 (10-11 m3 N-1 s-1) either in the case when the driving force is the capillary force due to the boundary energy or when it is the stored energy of dislocations.

scholarly journals Structure and Behaviour of Grain Boundaries in Polycrystalline Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 589-605 ◽  
Author(s):  
Akira Higashi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Moving Boundary ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Geometrical Model ◽  
Grain Boundary Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polycrystalline Ice

Abstract Recent progress in studies of the structure and behaviour of grain boundaries in ice are reviewed. As a lattice geometrical model of the boundary, the coincidence-site lattice (CSL) model is considered for ice crystals. Some evidence of the validity of this model is presented through observations of special shapes of natural snow, results of grain-boundary energy measurements, and direct microscopic observations of boundaries by X-ray diffraction topography. Although methods of measurement of grain-boundary energy have been developed recently, results are still not adequate to be analysed in terms of real energetics for comparison with models of atomic bonding. Modern methods of observing grain boundaries in ice using X-ray diffraction topography are described. Observations of migrating boundaries have revealed that faceting along most closely packed CSL points impede the migration of the CSL boundaries whilst increased numbers of steps among facets with boundaries of other kinds enhance it. The mobility of a fast-moving boundary has been determined to be of the order of 10-10 cm3 dyn-1 s-1 (10-11 m3 N-1 s-1) either in the case when the driving force is the capillary force due to the boundary energy or when it is the stored energy of dislocations.

Grain Boundary Defects in ZnO Ceramic Doped with Mo

2005 ◽  
Vol 242-244 ◽  
pp. 107-114 ◽  
Author(s):  
M. El-Hofy
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Electron Tunneling ◽  
Boundary Region ◽  
Chemical Formula ◽  
X Ray Diffraction ◽  
X Ray ◽  
Donor Density ◽  
Ceramic Samples ◽  
And Shifts

Four Zinc Molybdenum ceramic samples (S1-S4), have been prepared according to the chemical formula (1-x) ZnO - x (MoO3), where (x = 0.1, 0.2, 0.6, 0.8) mol %. The samples were studied through X-ray Diffraction analysis, SEM, EDAX, I-V characteristics at different temperature up to 200 οC and C-V measurements. X-ray results decleared that Mo contributes to the structure mainly substitution in place of Zn. Entrance of Mo into the structure increases the intensity and shifts the X-ray peaks to higher θ values. At lower additions, Mo is segregated along the grain boundaries in the form of short bars, while at higher additions, circular batches of Mo rich phase are appeared on the surface of the large ZnO grains. The formulation of Schottky barrier is indicated, in case of (x < 0.1) the barrier is attributed to the trapping of electrons by the defects at the grain boundaries, while at higher additions the barrier was attributed to the concentration gradient of Zn vacancies in the grain boundary region. The calculated barrier height and non-linearity coefficient α are (1.15, 1.12, 1.15 and 1.48) eV and (59.4, 22.5, 35 and 87) for the samples S1- S4 respectively. Going from S1 to S4, donor density Nd and density of the interface states Ns decrease from 3.81x 1018 to 0.46x1018 cm-3 and from 6.41x1012 to 2.52x1012 cm-2 respectively, while the width W(cm) of the potential barrier increases from the value 1.68x10-6 cm for S1 to the value 5.5x10-6 cm for S4 . The current processed via electron tunneling through the barrier.

STUDY OF THE DEPENDENCE OF HIGH Tc ON VARIOUS SINTERING TEMPERATURES FOR Bi-Pb-Sr-Ca-Cu-O SUPERCONDUCTORS

1991 ◽  
Vol 05 (24n25) ◽  
pp. 1635-1638
Author(s):  
S.M. M.R. NAQVI ◽  
A.A. QIDWAI ◽  
S.M. ZIA-UL-HAQUE ◽  
FIROZ AHMAD ◽  
S.D.H. RIZVI ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Liquid Nitrogen ◽  
X Ray Diffraction ◽  
High Tc ◽  
X Ray ◽  
Resistivity Measurements ◽  
Zero Resistance

Bi1.7-Pb0.3-Sr2-Ca2-Cu3-Ox superconducting samples were prepared at 855°C, 862 C, 870 C, and 882 C sintering temperatures respectively. All samples were sintered for 120 hours. The samples were then quenched in liquid nitrogen. The electrical resistivity measurements showed that the samples sintered at 870° C had the best Tc. For these samples the Tc onset was around 120 K and the zero resistance was obtained at 108 K. X-ray diffraction studies showed that the samples were multiphased.

X-ray diffraction study of the structure of various melts of the iron-germanium system in the liquid state

1978 ◽  
Vol 19 (1) ◽  
pp. 154-156
Author(s):  
V. P. Kazimirov ◽  
G. I. Batalin ◽  
E. S. Levin ◽  
V. �. Sokol'skii ◽  
V. A. Shovskii
Keyword(s):  
Diffraction Study ◽  
Liquid State ◽  
X Ray Diffraction ◽  
X Ray

Structural and thermodynamic properties of nanocrystalline fcc metals prepared by mechanical attrition

1992 ◽  
Vol 7 (7) ◽  
pp. 1751-1761 ◽  
Author(s):  
J. Eckert ◽  
J.C. Holzer ◽  
C.E. Krill ◽  
W.L. Johnson
Keyword(s):  
Thermal Analysis ◽  
Grain Size ◽  
Melting Point ◽  
Grain Boundary ◽  
Bulk Modulus ◽  
Atomic Level ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fcc Metals ◽  
Mechanical Attrition

Nanocrystalline fcc metals have been synthesized by mechanical attrition. The crystal refinement and the development of the microstructure have been investigated in detail by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The deformation process causes a decrease of the grain size of the fcc metals to 6–22 nm for the different elements. The final grain size scales with the melting point and the bulk modulus of the respective metal: the higher the melting point and the bulk modulus, the smaller the final grain size of the powder. Thus, the ultimate grain size achievable by this technique is determined by the competition between the heavy mechanical deformation introduced during milling and the recovery behavior of the metal. X-ray diffraction and thermal analysis of the nanocrystalline powders reveal that the crystal size refinement is accompanied by an increase in atomic-level strain and in the mechanically stored enthalpy in comparison to the undeformed state. The excess stored enthalpies of 10–40% of the heat of fusion exceed by far the values known for conventional deformation processes. The contributions of the atomic-level strain and the excess enthalpy of the grain boundaries to the stored enthalpies are critically assessed. The kinetics of grain growth in the nanocrystalline fcc metals are investigated by thermal analysis. The activation energy for grain boundary migration is derived from a modified Kissinger analysis, and estimates of the grain boundary enthalpy are given.

A High-Temperature Study of Phase Precipitation in Superalloys

1959 ◽  
Vol 3 ◽  
pp. 365-375
Author(s):  
John F. Radavich
Keyword(s):  
Heat Treatment ◽  
Electron Diffraction ◽  
Grain Boundaries ◽  
Fluorescence Analysis ◽  
Phase Precipitation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Suitable Heat Treatment ◽  
Nickel Base ◽  
High Temperature Study

AbstractMany of the iron- and nickel-base superalloys exhibit brittle properties on heat treatment, welding, or other fabrication processes at temperatures of about 2000°F or higher. Studies have been carried out by means of electron microscopy, electron diffraction, and X-ray diffraction and fluorescence analysis of the precipitation in the metal and in an isolated form.Results of the electron microscope study of the surface of the metal show a grain boundary constituent to be present which increases in amount as the temperature is increased. Studies on the isolated residue of such samples show a very thin “featherlike” film to be located at the grain boundaries and enclosing the grains. Electron diffraction, X-ray diffraction, and X-ray fluorescence analysis studies of the thin films indicate that they are a TiC phase with very little alloying elements in solution.At temperatures above 2000°F the thin film becomes quite thick and tends to force the grains apart. It is believed that this form of the TiC phase promotes the severe embrittling nature of these alloys at high temperatures. Suitable heat treatment at lower temperatures causes the TiC film to agglomerate and the grain boundaries become “tight,” and a more ductile condition results.

Structural and phase equilibria studies in the system Pt-Fe-Cu and the occurrence of tulameenite (Pt2FeCu)

1985 ◽  
Vol 49 (353) ◽  
pp. 547-554 ◽  
Author(s):  
M. Shahmiri ◽  
S. Murphy ◽  
D. J. Vaughan
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Critical Temperature ◽  
Grain Boundary ◽  
Phase Region ◽  
X Ray Diffraction ◽  
Two Phase ◽  
Slow Cooling ◽  
X Ray ◽  
Diffraction Patterns

AbstractThe crystal structure and compositional limits of the ternary compound Pt2FeCu (tulameenite), formed either by quenching from above the critical temperature of 1178°C or by slow cooling, have been investigated using X-ray diffraction, transmission electron microscopy, differential thermal analysis and electron probe microanalysis.The crystal structure of Pt2FeCu, established using electron density maps constructed from the measured and calculated intensities of X-ray diffraction patterns of powdered specimens, has the (000) and (½½0) lattice sites occupied by Pt atoms and the (½0½) and (0½½) sites occupied by either Cu or Fe atoms in a random manner. The resulting face-centred tetragonal structure undergoes a disordering transformation at the critical temperature to a postulated non-quenchable face-centred cubic structure. Stresses on quenching, arising from the ordering reaction, are relieved by twinning along {101} planes or by recrystallization along with deformation twinning; always involving grain boundary fracturing.Phase relations in the system Pt-Fe-Cu have been investigated through the construction of isothermal sections at 1000 and 600°C. At 1000°C there is an extensive single phase region of solid solution around Pt2FeCu and extending to the binary composition PtFe. At 600°C the composition Pt2FeCu lies just outside this now reduced area of solid solution in a two-phase field. Comparison of the experimental results with data for tulameenite suggests that some observed compositions may be metastably preserved. The occurrence of fine veinlets of silicate or other gangue minerals in tulameenite is suggested to result from grain boundary fracturing on cooling below the critical temperature of 1178°C and to be evidence of a magmatic origin.

Effect of Magnetic Field on Solidification Behavior of a MnCu Damping Alloy

2018 ◽  
Vol 279 ◽  
pp. 35-43 ◽  
Author(s):  
Ze Chao Jiang ◽  
Fan Yang ◽  
Jian Lan ◽  
Qing Chao Tian ◽  
Wei Dong Xuan ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Deflection Angle ◽  
Primary Dendrite ◽  
Metallographic Analysis ◽  
Coupling Mechanism ◽  
Solidification Behavior ◽  
X Ray Diffraction ◽  
X Ray ◽  
Variation Tendency

Preparation of Mn-Cu based damping alloy ingots coupled with strong magnetic fields shows many interesting phenomena on the solidification microstructure and the crystal lattice. In this study, modified M2052 ingots were prepared under different magnetic fields to investigate the bulk solidification behavior by using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Metallographic analysis reveals that the deflection angle of the primary dendrite arm increases with the increase of magnetic field strength. The distribution of chemical composition characterized by X-ray Fluorescence discloses that Mn is enriched while Cu is depleted along the circumferential surface side, and the variation tendency changes from almost a level to a sloping line under applied magnetic field. High magnetic field have altered the orientation of the γ-Mn dendrites from (200) to (111), and the coupling mechanism of alloy solidification with strong magnetic field is discussed based on the experimental results.

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