Stability of the Pd-Co-Ni-Cu-P Metallic Glasses

2007 ◽  
Vol 1048 ◽  
Author(s):  
Daisuke Fukamaki ◽  
Tsunehiro Takeuchi ◽  
Masashi Hasegawa ◽  
Kazuo Soda ◽  
Hirokazu Sato ◽  
...  
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Free Energy ◽  
Electronic Structure ◽  
Metallic Glass ◽  
Internal Energy ◽  
Metallic Glasses ◽  
Photoemission Spectroscopy ◽  
First Principle ◽  
Cluster Calculations

AbstractStability of Pd-Co-Ni-Cu-P metallic glass was investigated in terms of free energy using first principle cluster calculations, thermal analysis, and photoemission spectroscopy measurements. We found that the internal energy of the Pd-based metallic glasses is dominated by the electronic structure near the Fermi level. The analyses on the electronic structure and local atomic arrangements indicate that the substitution of cobalt or a hypothetical atom Co0.5Cu0.5 for nickel in the Pd40Ni40P20 metallic glass decreases the free energy of the Pd-Ni-P metallic glass by increasing entropy without altering significantly internal energy. On the basis of the idea mentioned above, we prepared Pd28Co24Ni24P24, Pd25Co25Ni25P25 and Pd40Co40/3Ni40/3Cu40/3P20 metallic glasses. These metallic glasses certainly showed the nearly highest TX, which directly reflect the activation energy against crystallization, among the Pd-based metallic glasses ever reported.

SURFACE AND VOLUME CRYSTALLIZATION OF METALLIC GLASS (Ni50Zr50)99.9P0.1 AS INVESTIGATED BY EXOELECTRON EMISSION (EEE) AND DIFFERENTIAL THERMAL ANALYSIS (DTA)

2002 ◽  
Vol 16 (03) ◽  
pp. 87-92 ◽  
Author(s):  
CZ. GÓRECKI ◽  
T. GÓRECKI ◽  
S. SZYMURA
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Differential Scanning Calorimetry ◽  
Differential Thermal Analysis ◽  
Metallic Glass ◽  
Heating Rate ◽  
Surface Crystallization ◽  
Exoelectron Emission ◽  
Ozawa Method ◽  
Scanning Calorimetry

Surface and volume crystallization of amorphous, melt-quenched (Ni50Zr50)99.9P0.1 alloy has been investigated by measurements of the temperature dependencies of the intensity of photostimulated exoelectron emission (EEE) and by differential scanning calorimetry (DSC). A comparison of these dependencies enables one to assess the tendency of the investigated materials to premature surface crystallization. For the (Ni50Zr50)99.9P0.1 alloy the surface crystallization occurs at temperatures distinctly lower than that for the crystallization in bulk. The activation energy for the surface crystallization, determined by the Ozawa method, i.e. from the shift of EEE peak corresponding to the surface crystallization on changing the heating rate, is also much lower than that for the volume crystallization.

Effect of Fe on Crystallization Process of Zr-Co-Al-(Fe) Bulk Metallic Glasses

2013 ◽  
Vol 745-746 ◽  
pp. 734-739 ◽  
Author(s):  
J. Tan ◽  
Fu Sheng Pan ◽  
C.J. Li ◽  
J.F. Wang ◽  
J. Eckert
Keyword(s):  
Activation Energy ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Metallic Glasses ◽  
Crystallization Process ◽  
Glass Forming Ability ◽  
Partial Replacement ◽  
Heat Of Mixing ◽  
Glass Forming ◽  
Internal States

The change in the internal states of Zr56Co28Al16 bulk metallic glass (BMG) upon minor substitution of Co with Fe was investigated for alloys with different compositions of Zr56Co28-xAl16Fex (x = 0, 1 and 2, respectively). Results exhibited that the ductile Zr-Co-Al-Fe BMGs were obtained and showed better glass-forming ability (GFA) via a small amount of Co partial replacement by Fe. In addition, the addition of a small amount of Fe enhanced the crystallization process and reduced the activation energy. The micro-alloying with Fe reduced the heat of mixing, which made the rearrangement of atoms easier during the crystallization process.

First and second laws of thermodynamics: relationship, “inconsistency”, hidden effects

2020 ◽  
pp. 63-73
Author(s):  
A. M. Savchenko ◽  
Yu. V. Konovalov ◽  
A. V. Laushkin
Keyword(s):  
Free Energy ◽  
Internal Energy ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Entropy Of Mixing ◽  
Ideal Mixing ◽  
Laws Of Thermodynamics ◽  
Relationship Of ◽  
The Relationship

The relationship of the first and second laws of thermodynamics based on their energy nature is considered. It is noted that the processes described by the second law of thermodynamics often take place hidden within the system, which makes it difficult to detect them. Nevertheless, even with ideal mixing, an increase in the internal energy of the system occurs, numerically equal to an increase in free energy. The largest contribution to the change in the value of free energy is made by the entropy of mixing, which has energy significance. The entropy of mixing can do the job, which is confirmed in particular by osmotic processes.

scholarly journals Electronic Structure of n-Cycloparaphenylenes Directly Observed by Photoemission Spectroscopy

2021 ◽  
Author(s):  
Kaname Kanai ◽  
Takuya Inoue ◽  
Takaya Furuichi ◽  
Kaito Shinoda ◽  
Takashi Iwahashi ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Electronic Structures ◽  
Photoemission Spectroscopy ◽  
Cyclic Structure ◽  
Visible Absorption ◽  
X Ray ◽  
Inverse Photoemission

A series of n-cycloparaphenylenes ([n]CPP) were studied by ultraviolet photoemission, inverse photoemission, ultraviolet-visible absorption, and X-ray photoemission spectroscopy to detect their unique electronic structures. [n]CPP has a cyclic structure in...

scholarly journals Tension-Tension Fatigue Behavior of High-Toughness Zr61Ti2Cu25Al12 Bulk Metallic Glass

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2815
Author(s):  
Yu Hang Yang ◽  
Jun Yi ◽  
Na Yang ◽  
Wen Liang ◽  
Hao Ran Huang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Shear Band ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Fatigue Resistance ◽  
Metallic Glasses ◽  
Stress Amplitude ◽  
Fatigue Behavior ◽  
Bulk Metallic Glasses ◽  
High Toughness

Bulk metallic glasses have application potential in engineering structures due to their exceptional strength and fracture toughness. Their fatigue resistance is very important for the application as well. We report the tension-tension fatigue damage behavior of a Zr61Ti2Cu25Al12 bulk metallic glass, which has the highest fracture toughness among BMGs. The Zr61Ti2Cu25Al12 glass exhibits a tension-tension fatigue endurance limit of 195 MPa, which is higher than that of high-toughness steels. The fracture morphology of the specimens depends on the applied stress amplitude. We found flocks of shear bands, which were perpendicular to the loading direction, on the surface of the fatigue test specimens with stress amplitude higher than the fatigue limit of the glass. The fatigue cracking of the glass initiated from a shear band in a shear band flock. Our work demonstrated that the Zr61Ti2Cu25Al12 glass is a competitive structural material and shed light on improving the fatigue resistance of bulk metallic glasses.

scholarly journals Boron Concentration Induced Co-Ta-B Composite Formation Observed in the Transition from Metallic to Covalent Glasses

2020 ◽  
Vol 5 (1) ◽  
pp. 18
Author(s):  
Simon Evertz ◽  
Stephan Prünte ◽  
Lena Patterer ◽  
Amalraj Marshal ◽  
Damian M. Holzapfel ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Metallic Glasses ◽  
Boron Concentration ◽  
High Strength ◽  
Point Of View ◽  
Composite Formation ◽  
Structural Applications ◽  
Glassy Materials ◽  
Metallic Bonding ◽  
Composite Region

Due to their unique property combination of high strength and toughness, metallic glasses are promising materials for structural applications. As the behaviour of metallic glasses depends on the electronic structure which in turn is defined by chemical composition, we systematically investigate the influence of B concentration on glass transition, topology, magnetism, and bonding for B concentrations x = 2 to 92 at.% in the (Co6.8±3.9Ta)100−xBx system. From an electronic structure and coordination point of view, the B concentration range is divided into three regions: Below 39 ± 5 at.% B, the material is a metallic glass due to the dominance of metallic bonds. Above 69 ± 6 at.%, the presence of an icosahedra-like B network is observed. As the B concentration is increased above 39 ± 5 at.%, the B network evolves while the metallic coordination of the material decreases until the B concentration of 67 ± 5 at.% is reached. Hence, a composite is formed. It is evident that, based on the B concentration, the ratio of metallic bonding to icosahedral bonding in the composite can be controlled. It is proposed that, by tuning the coordination in the composite region, glassy materials with defined plasticity and processability can be designed.

scholarly journals Synthesis of Bulk Zr48Cu36Al8Ag8 Metallic Glass by Hot Pressing of Amorphous Powders

2021 ◽  
Vol 5 (1) ◽  
pp. 23
Author(s):  
Tianbing He ◽  
Nevaf Ciftci ◽  
Volker Uhlenwinkel ◽  
Sergio Scudino
Keyword(s):  
Metallic Glass ◽  
Metallic Glasses ◽  
Flow Behavior ◽  
Matrix Composites ◽  
Powder Consolidation ◽  
Low Viscosity ◽  
Flash Annealing ◽  
Amorphous Powders ◽  
Temperature Window ◽  
Glass Matrix Composites

The critical cooling rate necessary for glass formation via melt solidification poses inherent constraints on sample size using conventional casting techniques. This drawback can be overcome by pressure-assisted sintering of metallic glass powders at temperatures above the glass transition, where the material shows viscous-flow behavior. Partial crystallization during sintering usually exacerbates the inherent brittleness of metallic glasses and thus needs to be avoided. In order to achieve high density of the bulk specimens while avoiding (or minimizing) crystallization, the optimal combination between low viscosity and long incubation time for crystallization must be identified. Here, by carefully selecting the time–temperature window for powder consolidation, we synthesized highly dense Zr48Cu36Ag8Al8 bulk metallic glass (BMG) with mechanical properties comparable with its cast counterpart. The larger ZrCu-based BMG specimens fabricated in this work could then be post-processed by flash-annealing, offering the possibility to fabricate monolithic metallic glasses and glass–matrix composites with enhanced room-temperature plastic deformation.

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