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S Rex - One of the best experts on this subject based on the ideXlab platform.
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coupled two phase α al θ al2cu planar growth and destabilisation along the univariant Eutectic Reaction in al cu ag alloys
Scripta Materialia, 2004Co-Authors: Jimmy De Wilde, Ludo Froyen, S RexAbstract:Abstract Coupled two-phase planar univariant Eutectic growth occurs in Al–Cu–Ag alloys for different compositions and over a range of solidification velocities along the univariant Eutectic Reaction L → α(Al) + θ(Al2Cu). The classical relationship λ2v=constant is obeyed. Two limits of stability are present: morphological stability and stability of the coupling.
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Organic alloy systems suitable for the investigation of regular binary and ternary Eutectic growth
Journal of Crystal Growth, 2004Co-Authors: Laszlo Sturz, Ulrike Hecht, V.t. Witusiewicz, S RexAbstract:Abstract Transparent organic alloys showing a plastic crystal phase were investigated experimentally using differential scanning calorimetry and directional solidification with respect to find a suitable model system for regular ternary Eutectic growth. The temperature, enthalpy and entropy of phase transitions have been determined for a number of pure substances. A distinction of substances with and without plastic crystal phases was made from their entropy of melting. Binary phase diagrams were determined for selected plastic crystal alloys with the aim to identify Eutectic Reactions. Examples for lamellar and rod-like Eutectic solidification microstructures in binary systems are given. The system ( d )Camphor–Neopentylglycol–Succinonitrile is identified as a system that exhibits, among others, univariant and a nonvariant Eutectic Reaction. The ternary Eutectic alloy close to the nonvariant Eutectic composition solidifies with a partially faceted solid–liquid interface. However, by adding a small amount of Amino-Methyl-Propanediol (AMPD), the temperature of the nonvariant Eutectic Reaction and of the solid state transformation from plastic to crystalline state are shifted such, that regular Eutectic growth with three distinct nonfaceted phases is observed in univariant Eutectic Reaction for the first time. The ternary phase diagram and examples for Eutectic microstructures in the ternary and the quaternary Eutectic alloy are given.
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Coupled two-phase [α(Al) + θ(Al2Cu)] planar growth and destabilisation along the univariant Eutectic Reaction in Al–Cu–Ag alloys
Scripta Materialia, 2004Co-Authors: Jimmy De Wilde, Ludo Froyen, S RexAbstract:Abstract Coupled two-phase planar univariant Eutectic growth occurs in Al–Cu–Ag alloys for different compositions and over a range of solidification velocities along the univariant Eutectic Reaction L → α(Al) + θ(Al2Cu). The classical relationship λ2v=constant is obeyed. Two limits of stability are present: morphological stability and stability of the coupling.
Ludo Froyen - One of the best experts on this subject based on the ideXlab platform.
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Microstructures Observed during Directional Solidification along the Univariant Eutectic Reaction in a Ternary Al-Cu-Si Alloy
Materials Science Forum, 2006Co-Authors: Jimmy De Wilde, Ludo FroyenAbstract:Within the frame of the ESA research program SETA, “Solidification along a Eutectic Path in Ternary Alloys”, experiments have been performed focussing on several distinct subtopics. One of these subtopics is to study coupled growth along the univariant Eutectic Reaction: L → α + β. In this paper, the influence of the growth velocity v on the morphology of the solid/liquid interface is evaluated in a ternary Al-Cu-Si alloy with a composition close to the univariant Eutectic groove L → α(Al) + θ-Αl2Cu. Different structural regions can be identified in terms of the stability of the solid-liquid interface (morphological stability) and the stability of the coupling (competitive growth) during unidirectional solidification as function of the solidification parameters. It is found that two-phase planar growth with a lamellar arrangement can be obtained at a sufficiently low growth rate v. The measured interlamellar spacing follows the Jackson and Hunt relationship λ2v = constant. At a higher growth velocity first a destabilisation of the solid/liquid interface is observed and finally competitive growth is observed revealing primary θ-Al2Cu growing ahead of the Eutectic interface. It is assumed that the cellular break-up is a two-step process related to the crystallography of the system. Fitting the different morphologies into one microstructure map, an extension of the coupled zone concept as has been proposed for binary alloys is necessary.
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Two-phase planar and regular lamellar coupled growth along the univariant Eutectic Reaction in ternary alloys: An analytical approach and application to the Al-Cu-Ag system
Journal of Applied Physics, 2005Co-Authors: J. De Wilde, Ludo Froyen, V. Witusiewicz, Ulrike HechtAbstract:Unidirectional solidification of ternary Eutectic alloys with a composition close to the univariant Eutectic Reaction under certain conditions leads to two-phase planar growth, showing a lamellar morphology similar to what is known from binary (invariant) Eutectic growth. In the latter case, the most applied analytical description is the Jackson–Hunt model. The present paper extends this model to steady-state two-phase planar and regular lamellar coupled growth in the case of the univariant Eutectic Reaction in ternary alloys as obtained during unidirectional solidification. It is shown that during steady state, a similar expression between the lamellar spacing λ and the growth velocity v, i.e., λ2v= constant, describes the spacing selection whenever minimum undercooling is assumed. The constant is only dependent on the material properties of the selected alloy. The theory is applied to growth along the univariant Reaction L→α(Al)+θ-Al2Cu in Al–Cu–Ag alloys resulting in a good agreement between the calcul...
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coupled two phase α al θ al2cu planar growth and destabilisation along the univariant Eutectic Reaction in al cu ag alloys
Scripta Materialia, 2004Co-Authors: Jimmy De Wilde, Ludo Froyen, S RexAbstract:Abstract Coupled two-phase planar univariant Eutectic growth occurs in Al–Cu–Ag alloys for different compositions and over a range of solidification velocities along the univariant Eutectic Reaction L → α(Al) + θ(Al2Cu). The classical relationship λ2v=constant is obeyed. Two limits of stability are present: morphological stability and stability of the coupling.
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Coupled two-phase [α(Al) + θ(Al2Cu)] planar growth and destabilisation along the univariant Eutectic Reaction in Al–Cu–Ag alloys
Scripta Materialia, 2004Co-Authors: Jimmy De Wilde, Ludo Froyen, S RexAbstract:Abstract Coupled two-phase planar univariant Eutectic growth occurs in Al–Cu–Ag alloys for different compositions and over a range of solidification velocities along the univariant Eutectic Reaction L → α(Al) + θ(Al2Cu). The classical relationship λ2v=constant is obeyed. Two limits of stability are present: morphological stability and stability of the coupling.
Jimmy De Wilde - One of the best experts on this subject based on the ideXlab platform.
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Microstructures Observed during Directional Solidification along the Univariant Eutectic Reaction in a Ternary Al-Cu-Si Alloy
Materials Science Forum, 2006Co-Authors: Jimmy De Wilde, Ludo FroyenAbstract:Within the frame of the ESA research program SETA, “Solidification along a Eutectic Path in Ternary Alloys”, experiments have been performed focussing on several distinct subtopics. One of these subtopics is to study coupled growth along the univariant Eutectic Reaction: L → α + β. In this paper, the influence of the growth velocity v on the morphology of the solid/liquid interface is evaluated in a ternary Al-Cu-Si alloy with a composition close to the univariant Eutectic groove L → α(Al) + θ-Αl2Cu. Different structural regions can be identified in terms of the stability of the solid-liquid interface (morphological stability) and the stability of the coupling (competitive growth) during unidirectional solidification as function of the solidification parameters. It is found that two-phase planar growth with a lamellar arrangement can be obtained at a sufficiently low growth rate v. The measured interlamellar spacing follows the Jackson and Hunt relationship λ2v = constant. At a higher growth velocity first a destabilisation of the solid/liquid interface is observed and finally competitive growth is observed revealing primary θ-Al2Cu growing ahead of the Eutectic interface. It is assumed that the cellular break-up is a two-step process related to the crystallography of the system. Fitting the different morphologies into one microstructure map, an extension of the coupled zone concept as has been proposed for binary alloys is necessary.
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coupled two phase α al θ al2cu planar growth and destabilisation along the univariant Eutectic Reaction in al cu ag alloys
Scripta Materialia, 2004Co-Authors: Jimmy De Wilde, Ludo Froyen, S RexAbstract:Abstract Coupled two-phase planar univariant Eutectic growth occurs in Al–Cu–Ag alloys for different compositions and over a range of solidification velocities along the univariant Eutectic Reaction L → α(Al) + θ(Al2Cu). The classical relationship λ2v=constant is obeyed. Two limits of stability are present: morphological stability and stability of the coupling.
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Coupled two-phase [α(Al) + θ(Al2Cu)] planar growth and destabilisation along the univariant Eutectic Reaction in Al–Cu–Ag alloys
Scripta Materialia, 2004Co-Authors: Jimmy De Wilde, Ludo Froyen, S RexAbstract:Abstract Coupled two-phase planar univariant Eutectic growth occurs in Al–Cu–Ag alloys for different compositions and over a range of solidification velocities along the univariant Eutectic Reaction L → α(Al) + θ(Al2Cu). The classical relationship λ2v=constant is obeyed. Two limits of stability are present: morphological stability and stability of the coupling.
Chin C Lee - One of the best experts on this subject based on the ideXlab platform.
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new solid state die attach method using silver foil bonded on aluminum substrate by Eutectic Reaction
Journal of Alloys and Compounds, 2019Co-Authors: Chin C LeeAbstract:Abstract The high thermal conductivity, lightweight, and low cost of aluminum (Al) make it a promising substrate material for high power electronic and photonic packages and housings. It is particularly attractive for aerospace and space applications due to its lightweight. A main challenge for these applications is poor bondability. The native aluminum oxide (Al2O3) prevents aluminum from bonding by using popular die-attach materials such as solders. Zincating process is often needed to dissolve the Al2O3 layer and deposit a protection zinc layer which provides a basis for subsequent metallization or soldering process. However, the zincating and metallization processes could increase the processing cost and bring more reliability issues. In this research, a novel Ag foil bonding technique has been developed to bond Ag foils directly to Al substrates to produce Ag-cladded Al substrates. Two Ag-Al bonding processes are developed: solid-state and Eutectic. Subsequently, Si chips are bonded to the Ag-cladded Al substrates using solid-state process at 300 °C without any additional die-attach material. For the Ag-Al bonding processes, no surface treatment is applied to Al substrates to remove the native Al2O3 layer. In the Ag-Al soli-state bonding process, Ag and Al atoms inter-diffused through the thin Al2O3 to react and form Ag2Al and Ag3Al compounds. In the Ag-Al Eutectic bonding process, Ag2Al+(Al) Eutectic structure forms at the Ag/Al interface without Ag3Al compound formation. The native Al2O3 layer, a potential fracture path, is broken into pieces during Eutectic Reaction and possibly dispersed into the Eutectic structure. Shear test results of Si/Ag/Al joint samples far exceed the military criterion (MIL-STD-883H method 2019.8). The Si/Ag/Al structures break either along the Ag/Al interface or within the Si chip. With the advantages of high thermal conductivity, high reliability, lightweight, and process simplicity, the Ag-cladded Al structures should be highly valuable for applications in packages and housings where lightweight and high heat-conducting are necessary.
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direct bonding silver to aluminum using Eutectic Reaction in air
Electronic Components and Technology Conference, 2018Co-Authors: Chin C LeeAbstract:The high thermal conductivity, light weight, and low cost of aluminum (Al) make it a promising substrate material for high power electronic packaging. Recently, direct bond aluminum (DBA) substrate has received significant attention as a possible alternative to direct bond copper (DBC) substrate which seems to have thermal cycling reliability issues. A main challenge of using aluminum substrates in electronic packaging is the poor bondability. The native aluminum oxide layer prevents aluminum from forming bonding with die-attach materials or metallization layers. Thus, zincating process is required to dissolve the aluminum oxide and deposit a protective layer of zinc, which provides a basis for subsequent metallization. In this research, Ag-Al Eutectic bonding has been developed as a novel bonding technique to direct bond Ag to Al substrate. The shear strength of the Ag-Al joints passes military criterion (MIL-STD-883H method 2019.8) with a large margin. SEM and TEM analyses were utilized to study the microstructures in details. The results reveal that Eutectic structure of Ag2Al and (Al) phase forms at the Ag/Al bonding interface. A uniform Ag2Al compound layer was observed between the Eutectic structure and Ag region, with no Ag3Al compound detected. In the Ag-Al Eutectic Reaction process, the aluminum oxide layer was broken into pieces and dispersed into the Eutectic structure region. To investigate the fracture modes of Ag-Al Eutectic joints, the fracture surfaces of Ag-Al joints were evaluated after the shear test. The fracture surfaces correspond to a typical ductile fracture with plastic deformation and drawing matrix. An application of this new technique is to bond Ag foils to Al substrates and make them bondable to die-attach materials such as solders and nano-silver paste. At a more advanced level, device chips can be bonded to the Ag foil on Al substrates at 300 °C using solid state bonding technique. This foil bonding application provides an alternative to the zincating and metallization processes on aluminum substrates. Other potential applications include making Al surfaces easier to blaze to other metals such as brass and copper.
Y Fang - One of the best experts on this subject based on the ideXlab platform.
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microstructural evolution in aisi 304 stainless steel during directional solidification and subsequent solid state transformation
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: J C, Yunliu Yang, Wei Tong, Y FangAbstract:The microstructural evolution during solidification and subsequent solid-state transformation of AISI 304 stainless steel is studied by directional solidification and quenching methods in this paper. The phase transformation sequence in the steel directionally solidified is that the precipitation of primary ferritic dendrites, ferrite-austenite Eutectic Reaction, and the direct formation of austenite occur in sequence during the directional solidification of the austenitic stainless steel. At the Eutectic Reaction stage, plenty of columnar and cellular Eutectic colonies composed of the coupled growth of lamellar ferrite and austenite take place. During the course of subsequent solid-state transformation, austenite grows into ferrite gradually, resulting in the disappearing of Eutectic colonies and thinning of primary ferritic dendrites, and dendrite cores of primary ferrite are retained as the final skeletal ferrite in the final microstructure. (c) 2006 Elsevier B.V. All rights reserved.
