Precipitation of icosahedral phase from amorphous Zr65Cu17.5−xAl7.5Ni10Agx (x = 0, 5) alloys

2001 ◽  
Vol 16 (5) ◽  
pp. 1311-1317 ◽  
Author(s):  
J. K. Lee ◽  
G. Choi ◽  
W. T. Kim ◽  
D. H. Kim
Keyword(s):  
Melt Spinning ◽  
Crystallization Behavior ◽  
Isothermal Transformation ◽  
Icosahedral Phase ◽  
Partial Replacement ◽  
Quasicrystalline Phase ◽  
Scanning Calorimetry ◽  
Crystallization Sequence ◽  
Transmission Electron ◽  
Injection Casting

Crystallization behavior of amorphous Zr65Cu17.5−xAl7.5Ni10Agx (x = 0, 5) alloys prepared by melt spinning and injection casting techniques has been studied using differential scanning calorimetry, x-ray diffractometry, and transmission electron microscopy. Ag addition changes crystallization sequence of the amorphous phase. The amorphous Zr65Cu17.5Al7.5Ni10 alloy crystallizes via simultaneous precipitation of icosahedral phase and NiZr2 phase in the first crystallization step whereas that in Zr65Cu12.5Al7.5Ni10Ag5 alloy crystallizes via precipitation of only icosahedral the phase. Partial replacement of Cu by Ag in Zr65Cu17.5Al7.5Ni10 alloy stabilized the icosahedral phase relative to competing intermetallic phases resulting in suppression of the precipitation of the NiZr2 phase, enhancement of the precipitation of icosahedral phase, and reduction of undercooled liquid range. Crystallization behavior of the amorphous Zr65Cu12.5Al7.5Ni10Ag5 alloy is not affected by cooling rate during solidification. Johnson–Mehl–Avrami analysis of isothermal transformation data suggests that the formation of the quasicrystalline phase is not entirely polymorphic in nature and may involve partitioning of the solute at later state.

Precipitation of icosahedral quasicrystalline phase in Hf69.5Al7.5Ni11Cu12 metallic glass

2001 ◽  
Vol 16 (4) ◽  
pp. 1190-1194 ◽  
Author(s):  
Chunfei Li ◽  
Akihisa Inoue
Keyword(s):  
Metallic Glass ◽  
Melt Spinning ◽  
Crystallization Process ◽  
Exothermic Reaction ◽  
Quasicrystalline Phase ◽  
Scanning Calorimetry ◽  
Exothermic Reactions ◽  
Transmission Electron ◽  
Icosahedral Quasicrystalline Phase ◽  
Icosahedral Quasicrystalline

A Hf69.5Al7.5Ni11Cu12 metallic glass was prepared by a single roller melt-spinning method, and the crystallization process was studied by x-ray diffraction, differential scanning calorimetry, and transmission electron microscopy. The metallic glass crystallizes through three exothermic reactions. The low-temperature exothermic reaction corresponded to the precipitation of an icosahedral quasicrystalline phase. Further annealing at higher temperature led to the decomposition of the icosahedral quasicrystalline phase to other stable crystalline phases, indicating that the precipitated icosahedral quasicrystalline phase was in a metastable state. The crystallization process of the present alloy was compared with that of other Hf–Al–Ni–Cu alloys, and the reason for the precipitation of the icosahedral quasicrystalline phase was discussed.

Investigation of Structure and Properties of the Al–Y–Ni–Co–Cu Metallic Glasses

2002 ◽  
Vol 17 (5) ◽  
pp. 1014-1018 ◽  
Author(s):  
Dmitri V. Louzguine ◽  
Akihisa Inoue
Keyword(s):  
Electron Microscopy ◽  
Metallic Glasses ◽  
Crystallization Behavior ◽  
Supercooled Liquid ◽  
Partial Replacement ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron

The present paper reports the effect of partial replacement of Ni by Cu in the Al85Y8Ni5Co2 alloy. The studied alloys were produced by rapid solidification. Glass-formation, crystallization behavior, and stability of the supercooled liquid were studied by x-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. Partial replacement of Ni by Cu in the Al85Y8Ni5Co2 metallic glass caused formation of the nanoscale α–Al particles and resulted in a decrease in the crystallization temperature and disappearance of the supercooled liquid.

CRYSTALLIZATION BEHAVIOR OF AMORPHOUS TI-NI-CU ALLOY RIBBONS

2008 ◽  
Vol 01 (02) ◽  
pp. 145-149 ◽  
Author(s):  
JUNG MIN NAM ◽  
YONG HEE LEE ◽  
TAE HYUN NAM ◽  
YEON WOOK KIM ◽  
JUNG MOO LEE
Keyword(s):  
Melt Spinning ◽  
Crystallization Behavior ◽  
Glass Forming Ability ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Cu Content ◽  
Glass Forming ◽  
Cu Alloy ◽  
Transmission Electron

Amorphous Ti 50 Ni (50-x) Cu x (at.%) (x = 15, 20 and 25) alloy ribbons were prepared by melt spinning, and then their crystallization behavior was investigated by optical microscopy, transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. Wavenumber (Qp) decreased from 29.40 nm-1 to 29.29 nm-1 and ΔT(T g - T x ) increased from 31 K to 36 K with increasing Cu content from 15 at.% to 25 at.%, suggesting that glass forming ability of Ti – Ni – Cu alloy ribbons increased with increasing Cu content. Activation energy for crystallization decreased from 211.5 kJ/mol to 136.4 kJ/mol with increasing Cu content from 15 at.% to 25 at.%, suggesting that a stability of Ti – Ni – Cu amorphous decreased with increasing Cu content.

Glass and Quasicrystal Formation in a Zr-based Multicomponent Alloy

2000 ◽  
Vol 644 ◽  
Author(s):  
U. Kühn ◽  
J. Eckert ◽  
N. Mattern ◽  
L. Schultz
Keyword(s):  
Amorphous Phase ◽  
Melt Spinning ◽  
Rapid Quenching ◽  
Quasicrystalline Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Copper Mold Casting ◽  
Transmission Electron ◽  
Mold Casting ◽  
Melt Spinning Technique

AbstractThe phase formation of a Zr57Ti8Nb2.5Cu13.9Ni11.1Al7.5alloy has been investigated upon cooling from the melt at different quenching rates as well as upon annealing of as-cast specimens. The different samples are characterized by x-ray diffraction, transmission electron microscopy and differential scanning calorimetry. Rapid quenching using the melt spinning technique results in amorphization. Slower cooling as realized upon copper mold casting leads to an icosaheadral quasicrystalline phase coexisting with a small amount of amorphous phase. The primarily formed quasicrystals have a grain size of about 1 νm. Upon annealing, the amorphous phase formed upon melt spinning precipitates quasicrystals in the first step of a series of transformations to the crystalline equilibrium compounds. The quasicrystals formed by annealing do not exceed a size of 5 to 10 nm.

On the Mechanical Milling of the AlCuFe Icosahedral Phase with Water

2014 ◽  
Vol 793 ◽  
pp. 23-27
Author(s):  
C. Patiño-Carachure ◽  
J. Luis López-Miranda ◽  
F. de la Rosa ◽  
M. Abatal ◽  
R. Pérez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Milling Time ◽  
Induction Furnace ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
X Ray Diffraction ◽  
Cast Sample ◽  
X Ray ◽  
Transmission Electron ◽  
Icosahedral Quasicrystalline

In this investigation the Al64Cu24Fe12 alloy was melted in an induction furnace and solidified under normal casting conditions. The as-cast sample was subject to a heat treatment at 700 oC under argon atmosphere in order to obtain the icosahedral quasicrystalline phase in a monophase region. Subsequently, the icosahedral phase was milled for different times and water added conditions. The pre-alloyed and milled powders were characterized using scanning electron microscopy, X-Ray diffraction, and transmission electron microscopy. The experimental results showed that the icosahedral phase is sensitive to the reaction between water and aluminum of the quasicrystalline alloy to generate hydrogen. As the milling time and the amount of water are increased, the embrittlement reaction of the alloy is accentuated releasing more hydrogen.

Quasicrystalline phase formation in Al62Cu22.5Fe12.5 and Al55Cu22.5Fe12.5Be7 alloys

2001 ◽  
Vol 16 (6) ◽  
pp. 1535-1540 ◽  
Author(s):  
S. M. Lee ◽  
B. H. Kim ◽  
D. H. Kim ◽  
W. T. Kim
Keyword(s):  
Heat Treatment ◽  
Icosahedral Phase ◽  
Partial Replacement ◽  
Quasicrystalline Phase ◽  
Icosahedral Structure ◽  
High Quality ◽  
Icosahedral Quasicrystalline Phase ◽  
Face Centered ◽  
Icosahedral Quasicrystalline ◽  
Conventionally Cast

Formation of the icosahedral quasicrystalline phase in conventionally cast Al62Cu25.5Fe12.5 and Al55Cu25.5Fe12.5Be7 alloys were investigated. The icosahedral phase (I-phase) forming ability was greatly improved by partial replacement of Al by 7 at.% Be. The as-cast Al55Cu25.5Fe12.5Be7 alloy consisted of dendritic primary I-phase and interdendritic τ-phase, whereas that of an as-cast Al62Cu25.5Fe12.5 alloy consisted of various phases such as the β-, I-, and τ-phases, together with a small amount of the λ- and η-phases. The kinetic barrier for transformation into single I-phase by heat treatment was greatly reduced in an Al55Cu25.5Fe12.5Be7 alloy. The I-phase in an Al55Cu25.5Fe12.5Be7 alloy has the same face centered icosahedral structure as that in an Al62Cu25.5Fe12.5 alloy and is of high quality without phason strain.

Crystallization of Al-Gd-La-Ni Metallic Glasses

1999 ◽  
Vol 580 ◽  
Author(s):  
T.K. Croat ◽  
A.K. Gangopadhyay ◽  
K.F. Kelton
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Metallic Glasses ◽  
Low Temperatures ◽  
Alloy Composition ◽  
Composition Range ◽  
Scanning Calorimetry ◽  
Crystallization Sequence ◽  
Transmission Electron ◽  
Kinetics Of

AbstractThe crystallization kinetics of Al-Gd-La-Ni metallic glasses to nanostructured phases are analyzed using differential scanning calorimetry and transmission electron microscopy. In a narrow alloy composition range near Al88Gd6La2Ni4, TEM reveals an amorphous phase separation that occurs upon annealing at low temperatures prior to crystallization. Al-enriched regions, typically 40 nm in diameter, bounded by rare-earth rich regions, are visible. Upon crystallization, α-Al forms preferentially at the interface between these phase separated regions. The relevance of this crystallization sequence to previous work in Al-RE-TM glasses and to the evolution of nanoscale microstructures common in the crystallization of other metallic glasses are discussed.

scholarly journals Phase Transformation of High Velocity Air Fuel (HVAF)-Sprayed Al-Cu-Fe-Si Quasicrystalline Coating

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 834
Author(s):  
Mingwei Cai ◽  
Jun Shen
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
Amorphous Phase ◽  
High Velocity ◽  
Quasicrystalline Phase ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Heating And Cooling ◽  
Transmission Electron ◽  
The Difference

Al-Cu-Fe-Si quasicrystalline coatings were prepared by high velocity air fuel spraying to study their phase transformation during the process. The feedstock powder and coating were phase characterized by scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry, and transmission electron microscopy. Results show that Al3Cu2 phase, a small amount of λ-Al13Fe4 phase, quasicrystalline phase (QC), amorphous phase, and β-Al (Cu, Fe, Si) phase were present in the sprayed Al50Cu20Fe15Si15 powder. For a typical flattened powder particle, the splat periphery was surrounded by a 1 µm thick amorphous phase. The inside area of the splat was composed of the QC covered by the Al3Cu2 and Si-rich β-Al (Cu, Fe, Si) phases. Another kind of Cu- rich β-Al (Cu, Fe, Si) phase can be found close to the amorphous area with a similar composition to the original β-Al (Cu, Fe, Si) phase in the powder. Different phases were observed when the periphery and inside area of the splat were compared. This result was caused by the difference in the heating and cooling rates.

scholarly journals High-Density Polyethylene Composites Filled with Nanosilica Containing Immobilized Nanosilver or Nanocopper: Thermal, Mechanical, and Bactericidal Properties and Morphology and Interphase Characterization

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Regina Jeziórska ◽  
Maria Zielecka ◽  
Beata Gutarowska ◽  
Zofia Żakowska
Keyword(s):  
High Density Polyethylene ◽  
Interfacial Adhesion ◽  
Crystallization Behavior ◽  
High Density ◽  
Melt Blending ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Bactericidal Properties ◽  
Excellent Activity ◽  
Thermal Stability Of

Silica containing immobilized nanosilver (Ag-SiO2) or nanocopper (Cu-SiO2) was used as a filler for high-density polyethylene (HDPE). The HDPE/Ag-SiO2and HDPE/Cu-SiO2composites were prepared by melt blending and injection molding. The microstructure of the composites was examined using transmission electron microscopy (TEM). The crystallization behavior and thermal properties were studied using differential scanning calorimetry (DSC) and thermogravimetry (TGA). The mechanical properties were characterized by tensile, flexural, and impact tests as well as dynamic mechanical thermal analysis (DMTA). The ability of silica to give antimicrobial activity to HDPE was also investigated and discussed. The TEM images indicate that Ag-SiO2show lower degree of agglomeration than Cu-SiO2nanoparticles. The crystallization temperature increased, whereas crystallinity decreased in the composites. The thermal stability of the composites was significantly better compared to HDPE. Improved stiffness indicating very good interfacial adhesion was observed. Excellent activity against different kinds of bacteria was found.

scholarly journals Local Order in Single Grain Cd-Yb Icosahedral Phase

2003 ◽  
Vol 805 ◽  
Author(s):  
Y. Q. Wu ◽  
M. J. Kramer ◽  
T. A. Lograsso
Keyword(s):  
Cluster Structure ◽  
Icosahedral Phase ◽  
Quasicrystalline Phase ◽  
Local Order ◽  
Local Cluster ◽  
Transmission Electron Microcopy ◽  
Transmission Electron ◽  
Single Grain ◽  
Matching Rules ◽  
D Model

ABSTRACTSingle grains of icosahedral Cd84Yb16 quasicrystalline phase were characterized using high resolution transmission electron microcopy (HRTEM) technique. Image reconstruction of the obtained multiple through-focal series for both the two and five-fold axes are consistent with the local cluster structure of concentric polyhedra consisting of Cd tetrahedron (1/3 occupied icosahedron), Cd dodecahedron, Yb icosahedron and a Cd icosidodecahedron. Edge-sharing of the clusters can result in complete tiling of the 2-D projections. Simple matching rules are being investigated to construct a 3-D model.

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