In Situ Observation of the Chemical Bonding State of Si in the Molten State of Eutectic Au-Si alloy of Au81Si19 by Using a Soft X-ray Emission Spectroscopy Electron Microscope

Microscopy ◽  
2021 ◽  
Author(s):  
Masami Terauchi ◽  
Naoya Umemoto ◽  
Yohei Sato ◽  
Masaki Ageishi ◽  
An-Pang Tsai
Keyword(s):  
Melting Temperature ◽  
Energy State ◽  
Alloy System ◽  
Intensity Profile ◽  
In Situ Observation ◽  
Molten State ◽  
Density Of State ◽  
Large Drop ◽  
Calculated Density ◽  
Atomic Arrangement

Abstract Phase diagram of Au-Si binary alloy system shows a large drop of melting temperature of about 1000 K compared with that of Si at a composition of Au:Si=81:19, where the melting temperature is about 636 K. Mixing of Au and Si below the melting temperature was observed by transmission electron microscopy experiment and found the mixed region show a diffraction pattern of a diffuse ring intensity indicating an amorphous structure of the mixed area. Si L-emission spectra, which reflects the energy state of bonding electrons of Si atom, of molten Au81Si19 alloy was measured for the first time to investigate the energy state of valence electrons of Si. The Si L-emission spectrum showed a characteristic loss of L1 peak, which is related to sp3 directional bonding in crystalline Si. The intensity profile is also different from that of molten Si reported. This suggests a characteristic atomic arrangement exist in the molten state. The intensity profile also indicated a small density of state in the molten state at Fermi energy. The obtained spectrum was compared with the calculated density of state of possible crystal structures reported. The comparison suggested that Si atoms are surrounded by 8 Au atoms in the molten state of Au81Si19 alloy. The formation of this local atomic arrangement can be an origin of a large drop of melting temperature at about Au:Si=81:19.

Thermodynamic and Kinetic Studies of Pulsed-Laser Annealing from Transient Conductivity Measurements

1984 ◽  
Vol 35 ◽  
Author(s):  
P.S. Peercy ◽  
Michael O. Thompson
Keyword(s):  
Melting Temperature ◽  
Silicon Germanium ◽  
Laser Annealing ◽  
Pulsed Laser ◽  
Kinetic Studies ◽  
Alloy System ◽  
Velocity Versus ◽  
Solidification Velocity ◽  
Molten Layer ◽  
Amorphous Si

ABSTRACTSimultaneous measurements of the transient conductance and time-dependent surface reflectance of the melt and solidification dynamics produced by pulsed laser irradiation of Si are reviewed. These measurements demonstrate that the melting temperature of amorphous Si is reduced 200 ± 50 K from that of crystalline Si and that explosive crystallization in amorphous Si is mediated by a thin (≤ 20 nm) molten layer that propagates at ~ 15 m/sec. Studies with 3.5 nsec pulses permit an estimate of the dependence of the solidification velocity on undercooling. Measurements of the effect of As impurities on the solidification velocity demonstrate that high As concentrations decrease the melting temperature of Si (~ 150 K for 7 at.%), which can result in surface nucleation to produce buried melts. Finally, the silicon-germanium alloy system is shown to be an ideal model system for the study of superheating and undercooling. The Si50Ge50 alloy closely models amorphous Si, and measurements of layered Si-Ge alloy structures indicate superheating up to 120 K without nucleation of internal melts. The change in melt velocity with superheating yields a velocity versus superheating of 17 ± 3 k/m/sec.

A novel Zr-Ti-Ni-Cu eutectic system with low melting temperature for the brazing of titanium alloys near 800 °C

2010 ◽  
Vol 25 (2) ◽  
pp. 296-302 ◽  
Author(s):  
Ju-Hyun Sun ◽  
Dong-Myoung Lee ◽  
Chi-Hwan Lee ◽  
Joo-Wha Hong ◽  
Seung-Yong Shin
Keyword(s):  
Melting Temperature ◽  
Eutectic Alloy ◽  
Ternary Eutectic ◽  
Pure Titanium ◽  
Alloy System ◽  
Eutectic Structure ◽  
Eutectic System ◽  
Alloy Sample ◽  
Commercially Pure Titanium ◽  
Cu Content

This article reports on low (below 800 °C) melting temperature characteristics of a Zr-Ti-Ni-Cu alloy system, designed by adding a small amount of Cu to a Zr-Ti-Ni eutectic alloy system in the Zr-rich corner of the Zr-Ti-Ni system. A series of Zr-Ti-Ni-Cu-based alloy buttons of varying Cu content was fabricated by an arc melting machine. The melting temperature ranges of the quaternary alloys were systematically examined by differential thermal analysis (DTA). As a result, a quaternary eutectic alloy of composition Zr54Ti22Ni16Cu8 with a low melting temperature range from 774 °C to 783 °C was found. In addition, structural and chemical analysis results for the slowly solidified, quaternary eutectic alloy sample revealed equivalent quaternary eutectic structure and phases to those of the ternary eutectic Zr50Ti26Ni24 alloy, except for a small amount of Cu dissolved in individual constituent phases. The wetting angle tested at 800 °C for 60 s on the commercially pure titanium was about 25°.

scholarly journals Explanation of the cluster structures melting mechanism and their influence on the molten state’s physical and chemical nature

2021 ◽  
Vol 316 (1) ◽  
pp. 62-68
Author(s):  
G. S. Shaikhova ◽  
Keyword(s):  
Temperature Dependence ◽  
Melting Temperature ◽  
Chemical Nature ◽  
Bethe Lattice ◽  
Molten State ◽  
Melt Temperature ◽  
Metal Melts ◽  
Cluster Fragmentation ◽  
Melting Mechanism ◽  
Physical And Chemical

There are results of the melts of semimetals and semiconductors of various structural groups research in the article. On the example of simplified regular Bethe lattice one can model destruction and aggregation of structures in clusters and on it’s basis to substantiate the metal melts properties in the form of nanolayers. The variety of compressibility polytherms forms in electronic melts requires typing, since their analysis makes it possible to explain the mechanism of the aggregation and dissolution processes of extended objects in melts. The article contains formulas that allow explaining the mechanism of the dissolution of cluster structures and their influence on the physicochemical nature of the molten state. There is considered the process of cluster fragmentation. Larger fragments of clusters are formed in the process of crushing, and this fact leads to the compressibility that decreases more rapidly, only after passing through the extremum it begins to increase due to the thermal loosening. The study of the function's compressibility for an extremum in the compressibility's temperature dependence also indicates the changing process of the clusters decomposition mechanisms in melts with an increase in temperature and vice versa to aggregation with a decrease in the melt temperature to the melting temperature.

scholarly journals A Study of Low Young’s Modulus Ti–15Ta–15Nb Alloy Using TEM Analysis

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5694
Author(s):  
Huey-Er Lee ◽  
Ju-Hui Wu ◽  
Chih-Yeh Chao ◽  
Yen-Hao Chang ◽  
Je-Kang Du ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Alloy System ◽  
Lattice Parameters ◽  
Microstructural Characteristics ◽  
Tem Analysis ◽  
Structural Class ◽  
Atomic Arrangement ◽  
Xrd And Tem

The microstructural characteristics and Young’s modulus of the as-cast Ti–15Ta–15Nb alloy are reported in this study. On the basis of the examined XRD and TEM results, the microstructure of the current alloy is essentially a mixture (α + β+ α′ + α″ + ω + H) phase. The new H phase has not previously been identified as a known phase in the Ti–Ta–Nb alloy system. On the basis of examination of the Kikuchi maps, the new H phase belongs to a tetragonal structural class with lattice parameters of a = b = 0.328 nm and c = 0.343 nm, denoting an optimal presentation of the atomic arrangement. The relationships of orientation between these phases would be {0001}α//{110}β//{1¯21¯0}ω//{101¯}H and (011¯0)α//(11¯2)β//(1¯010)ω//(121)H. Moreover, the Young’s modulus of the as-cast Ti–15Ta–15Nb alloy is approximately E = 80.2 ± 10.66 GPa. It is implied that the Young’s modulus can be decreased by the mixing of phases, especially with the presence of the H phase.

First-principles calculations for point defects in MAX phases Ti2AlN

2016 ◽  
Vol 30 (09) ◽  
pp. 1650101 ◽  
Author(s):  
Yaowen Zhang ◽  
Shutong Yang ◽  
Canglong Wang
Keyword(s):  
Point Defects ◽  
First Principles ◽  
First Principles Calculations ◽  
Density Of State ◽  
Max Phases ◽  
Calculated Density ◽  
Software And Hardware ◽  
General Physical ◽  
Computational Resources ◽  
Good Agreement

This paper outlines general physical issues associated with performing computational numerical simulations of primary point defects in MAX phases Ti2AlN. First-principles solutions are possible due to the development of computational resources of software and hardware. The calculation accuracy is a good agreement with the experimental results. As an important application of our simulations, the results could provide a theoretical guidance for future experiments and application of Ti2AlN. For example, the N mono-vacancy is the most difficult to form. On the contrary, the mono-vacancy formation in Ti2AlN is energetically most favorable for the Al atom. The essence of the phenomena is explained by the calculated density of state (DOS).

scholarly journals Solidification Microstructures of the Ingots Obtained by Arc Melting and Cold Crucible Levitation Melting in TiNbTaZr Medium-Entropy Alloy and TiNbTaZrX (X = V, Mo, W) High-Entropy Alloys

Entropy ◽  
2019 ◽  
Vol 21 (5) ◽  
pp. 483 ◽  
Author(s):  
Takeshi Nagase ◽  
Kiyoshi Mizuuchi ◽  
Takayoshi Nakano
Keyword(s):  
Melting Temperature ◽  
Alloy System ◽  
Distribution Coefficients ◽  
Thermodynamic Calculations ◽  
High Entropy Alloys ◽  
Cold Crucible ◽  
High Entropy ◽  
Arc Melting ◽  
Significant Difference ◽  
Solidification Microstructures

The solidification microstructures of the TiNbTaZr medium-entropy alloy and TiNbTaZrX (X = V, Mo, and W) high-entropy alloys (HEAs), including the TiNbTaZrMo bio-HEA, were investigated. Equiaxed dendrite structures were observed in the ingots that were prepared by arc melting, regardless of the position of the ingots and the alloy system. In addition, no significant difference in the solidification microstructure was observed in TiZrNbTaMo bio-HEAs between the arc-melted (AM) ingots and cold crucible levitation melted (CCLM) ingots. A cold shut was observed in the AM ingots, but not in the CCLM ingots. The interdendrite regions tended to be enriched in Ti and Zr in the TiNbTaZr MEA and TiNbTaZrX (X = V, Mo, and W) HEAs. The distribution coefficients during solidification, which were estimated by thermodynamic calculations, could explain the distribution of the constituent elements in the dendrite and interdendrite regions. The thermodynamic calculations indicated that an increase in the concentration of the low melting-temperature V (2183 K) leads to a monotonic decrease in the liquidus temperature (TL), and that increases in the concentration of high melting-temperature Mo (2896 K) and W (3695 K) lead to a monotonic increase in TL in TiNbTaZrXx (X = V, Mo, and W) (x =  0 − 2) HEAs.

scholarly journals In situ observation of the impact of hydrogen bubbles in Al–Cu melt on directional dendritic solidification

2021 ◽  
Vol 56 (13) ◽  
pp. 8225-8242
Author(s):  
T. Werner ◽  
M. Becker ◽  
J. Baumann ◽  
C. Pickmann ◽  
L. Sturz ◽  
...  
Keyword(s):  
Solidification Front ◽  
Bubble Diameter ◽  
Alloy System ◽  
Local Variation ◽  
Bubble Nucleation ◽  
In Situ Observation ◽  
Cu Alloy ◽  
Solidification Speed ◽  
The Impact

AbstractMuch research has already been focused on the solid-bubble interaction in the interdendritic space for solidifying materials. However, commonly, bubble nucleation is not limited to the mushy zone but also occurs in the liquid melt. In the present research on an Al-$$10 \, \%\mathrm {wt. \,}$$ 10 % wt . Cu alloy, the interaction between these bubbles and the approaching solidification front becomes apparent under in situ X-radiography and allows for new insights into the influence of bubbles on the solidifying microstructure. The observed effects comprise bulging of the solidification front toward the bubble, bending of dendrites in front of the bubble, coronal outgrowths surrounding the bubbles, as well as bubble growth, bubble pushing, and bubble eruption. It is found that for the present Al–Cu alloy, the local variation in the solidification speed can be attributed to the bubbles’ insulating properties. The range of this effect was observed to be up to $$900 \,\upmu \text {m}$$ 900 μ m , depending on the bubble diameter, locally increasing solidification speed by up to $$350 \, \%$$ 350 % . The influences of Marangoni vortices and coronal nucleation of misoriented dendrites around bubbles on the homogeneity of the microstructure are discussed. A comparison with experiments on model alloys and simulations from various other studies highlights the similarities and differences to this metallic alloy system.

Electronic Structures and Chemical Bonding of the Layered Tungsten Borides: An Ab Initio Calculation

2010 ◽  
Vol 434-435 ◽  
pp. 178-181 ◽  
Author(s):  
Xue Wen Xu ◽  
Yang Xian Li ◽  
Wei Bing Zhou ◽  
Jiao Qun Zhu ◽  
Bing Chu Mei
Keyword(s):  
Ab Initio ◽  
Chemical Bonding ◽  
Electronic Structures ◽  
Function Theory ◽  
Density Of State ◽  
Covalent Bonds ◽  
Calculated Density ◽  
Density Distributions ◽  
Ionic Bonds ◽  
Tungsten Borides

We have investigated the electronic structures and chemical bonding of four tungsten borides, including two WB2 compounds with different crystal structures, α-W2B5 and ε-WB2.5, by ab initio calculations based on density function theory (DFT). The calculated density of state (DOS) shows that all compounds are metallic. The DOS at Fermi level is mainly contributed from 5d states of W atoms. The strong covalent bonds of boron atoms make these compounds stable. Due to a lack of electrons in boron sublattices, weak ionic bonds are generated. The charge density distributions indicate the solid B layers or B polyhedrons are interleaved by the W layers.

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