Surface Alloys of Icosahedral AlMnSi with Phason Distortions

1986 ◽  
Vol 74 ◽  
Author(s):  
D. M. Follstaedt ◽  
J. A. Knapp
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Ion Beam ◽  
Icosahedral Phase ◽  
The Novel ◽  
Ion Beam Mixing ◽  
Si Substrates ◽  
Formation Kinetics ◽  
Icosahedral Phases ◽  
Diffraction Patterns

AbstractThe microstructures produced by electron-beam melting and by ion-beam mixing Al/Mn and Al/Mn/Si layers on Si substrates are examined. The treatments were found to incorporate Si from the substrate into the surface alloy. Several phases formed, depending on treatment, including α- and β-AlMnSi, μ-AlMn (epitaxial on Si{111}), and amorphous and icosahedral AlMnSi. The observed microstructures relate the novel icosahedral phase to other phases and elucidate its formation kinetics. Diffraction patterns from large icosahedral grains (up to 5 μm) show distortions in the position and shape of weak (but not strong) reflections, as predicted for phason defects in a quasicrystalline lattice, one of the structures proposed for icosahedral phases.

Formation of Surface Layers of Icosahedral Al(Mn)

1985 ◽  
Vol 51 ◽  
Author(s):  
J. A. Knapp ◽  
D. M. Follstaedt
Keyword(s):  
Electron Beam ◽  
Solid State ◽  
Ion Beam ◽  
Icosahedral Phase ◽  
Surface Layers ◽  
Melt Quenching ◽  
Ion Beam Mixing ◽  
State Diffusion ◽  
Laser Treatments ◽  
A New Technique

ABSTRACTSurface layers of the icosahedral phase of Al(Mn) have been formed from thin, alternating Al/Mn layers deposited on Al or Fe surfaces by rapid electron-beam or laser melting, by ion beam mixing, and by solid-state diffusion. The electron beam and laser treatments are similar to other liquid quenching techniques used previously to form the phase, but have well defined temperature histories which allow us to place limits on the melting point of the icosahedral phase, the time needed for its nucleation from the melt, and its growth velocity. Ion beam mixing is a way of forming the icosahedral phase which is quite different from melt quenching; the phase is formed during ion beam mixing at temperatures of 100–200°C. For mixing at ≤60C an amorphous phase with icosahedral short-range order is formed; this phase can be converted to the icosahedral phase by subsequent annealing. Formation of the icosahedral phase by reacting the as-deposited layers in the solid state is a new technique not previously reported. The results presented here place new restrictions on proposed structural and thermodynamic models for the icosahedral phase.

Formation of Quasicrystals In Rapidly Solidified Al Alloys

1985 ◽  
Vol 58 ◽  
Author(s):  
Robert J. Schaefer ◽  
Leonid A Bendersky
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Icosahedral Phase ◽  
Intermetallic Phases ◽  
Moderate Growth ◽  
Wide Range ◽  
Beam Surface ◽  
Equilibrium Phases ◽  
Rapidly Solidified ◽  
T Phase

ABSTRACTElectron beam surface melting has been used to study Al-Mn and Al-Mn-Si alloys subjected to a wide range of solidification conditions. Several of the reported equilibrium intermetallic phases are not found even at moderate growth rates. Beyond a composition-dependent critical velocity the equilibrium phases are all replaced by the quasicrystalline icosahedral and decagonal (T) phases. The icosahedral phase is favored over the T phase by higher solidification velocities. The addition of Si to Al-Mn alloys eliminates the T phase, but does not significantly facilitate the formation of the icosahedral phase by electron beam melting because the ternary α and β phases of Al-Mn-Si are able to grow rapidly into the electron beam melts.

Structure Transformations of the Decagonal and Icosahedral Phases in Quaternary Alloys.

1991 ◽  
Vol 235 ◽  
Author(s):  
R. Perez ◽  
J. Reyes-Gasga ◽  
M. Jose-Yacaman
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Transmission Electron Microscope ◽  
Icosahedral Phase ◽  
Electron Radiation ◽  
Quaternary Alloys ◽  
Decagonal Phase ◽  
Icosahedral Phases ◽  
Transmission Electron ◽  
Diffraction Patterns

ABSTRACTAn investigation of the phase transformations experienced by the decagonal and icosahedral phases in two different quaternary -alloys is carried out. The transformation in the decagonal phase of Al-Cu-Co-Si alloy is induced by the electron radiation in a transmission electron microscope. However, in the icosahedral phase of Al-Cu-Co-Fe alloy this transformation is induced by annealing. Electron diffraction patterns obtained from both phases suggest that the deformation mechanism involved in these kind of transitions is related with twinning

scholarly journals Characterization of Spatter and Sublimation in Alloy 718 during Electron Beam Melting

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 5953
Author(s):  
Ahmad Raza ◽  
Eduard Hryha
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Elevated Temperatures ◽  
Ion Beam ◽  
High Vacuum ◽  
Alloying Elements ◽  
Heat Shield ◽  
Alloy 718 ◽  
Feedstock Powder ◽  
Heat Shields

Due to elevated temperatures and high vacuum levels in electron beam melting (EBM), spatter formation and accumulation in the feedstock powder, and sublimation of alloying elements from the base feedstock powder can affect the feedstock powder’s reusability and change the alloy composition of fabricated parts. This study focused on the experimental and thermodynamic analysis of spatter particles generated in EBM, and analyzed sublimating alloying elements from Alloy 718 during EBM. Heat shields obtained after processing Alloy 718 in an Arcam A2X plus machine were analyzed to evaluate the spatters and metal condensate. Comprehensive morphological, microstructural, and chemical analyses were performed using scanning electron microscopy (SEM), focused ion beam (FIB), and energy dispersive spectroscopy (EDS). The morphological analysis showed that the area coverage of heat shields by spatter increased from top (<1%) to bottom (>25%), indicating that the spatter particles had projectile trajectories. Similarly, the metal condensate had a higher thickness of ~50 μm toward the bottom of the heat shield, indicating more significant condensation of metal vapors at the bottom. Microstructural analysis of spatters highlighted that the surfaces of spatter particles sampled from the heat shields were also covered with condensate, and the thickness of the deposited condensate depended on the time of landing of spatter particles on the heat shield during the build. The chemical analysis showed that the spatter particles had 17-fold higher oxygen content than virgin powder used in the build. Analysis of the metalized layer indicated that it was formed by oxidized metal condensate and was significantly enriched with Cr due to its higher vapor pressure under EBM conditions.

The effect of temperature on ion beam mixing of Mo films on Si substrates

Vacuum ◽  
1989 ◽  
Vol 39 (2-4) ◽  
pp. 259-261 ◽  
Author(s):  
Gao Wenyu ◽  
Li Hongcheng ◽  
Wang Ruilan ◽  
Liu Jiarui
Keyword(s):  
Ion Beam ◽  
Effect Of Temperature ◽  
Ion Beam Mixing ◽  
Si Substrates

A Novel Silicided Shallow Junction Technology for Cmos VLSI

1986 ◽  
Vol 71 ◽  
Author(s):  
D.L. Kwong ◽  
Y.H. Ku ◽  
S.K. Lee ◽  
N.S. Alvi ◽  
P. Chu ◽  
...  
Keyword(s):  
Low Temperature ◽  
Ion Beam ◽  
Electrical Characteristics ◽  
Ion Beam Mixing ◽  
Si Substrates ◽  
Novel Technique ◽  
Low Temperature Annealing ◽  
Vlsi Technology ◽  
Shallow Junctions ◽  
Cmos Vlsi

AbstractA novel technique for the fabrication of shallow, silicided p+-n junctions with excellent electrical characteristics has been developed. The technique utilizes the ion implantation of dopants into silicide layers formed by ion-beam mixing with Si ions and low temperature annealing, and the subsequent drive-in of implanted dopants into the Si substrates to form shallow junctions. This technique can be easily applied to the fabrication of MOSFETs in a self-aligned fashion, and can have a significant impact on CMOS VLSI technology.

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