Amorphous aluminum alloys—synthesis and stability

Perepezko, John H.; Hebert, Rainer J.

doi:10.1007/bf02822618

Cited by 85 publications

(67 citation statements)

References 39 publications

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“…Moreover, the optimized processing parameters were further validated via gas atomization of amorphous Al powder of Al 90 Gd 7 Ni 2 Fe 1 . Al-based metallic glasses (MGs), with content exceeded 85 at pct Al and containing transition metal (TM) and rare earth (RE) additions, have attracted much interest in recent years because of their low cost, low density, and attractive combinations of mechanical properties, [14][15][16] such as ultimate tensile strength values that have been reported to reach 1500 MPa combined with good ductility. [17,18] The selected Al 90 Gd 7 Ni 2 Fe 1 (at pct) is a dilute alloy, in which the solute content (TM + RE) is typically below 10 at pct.…”

Section: Introductionmentioning

confidence: 99%

Gas Atomization of Amorphous Aluminum Powder: Part II. Experimental Investigation

Zheng

Lin

Zhou

et al. 2009

Metall Mater Trans B

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The optimal processing parameters that are required to atomize amorphous Al were established on the basis of numerical simulations in part I of this study. In this part II, the characterization of cooling rate experienced by gas-atomized, Al-based amorphous powders was studied via experiments. An experimental investigation was implemented to validate the numerical predictions reported in part I of this study. The cooling rate experienced by the powders, for example, was experimentally determined on the basis of dendrite arm spacing correlations, and the results were compared with the numerical predictions. The experimental studies were completed using commercial Al 2024 as a baseline material and Al 90 Gd 7 Ni 2 Fe 1 metallic glass (MG). The results showed that the cooling rate of droplets increases with decreasing particle size, with an increasing proportion of helium in the atomization gas and with increasing melt superheat. The experimental results reported in this article suggest good agreement between experiments and numerical simulations.

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Section: Introductionmentioning

confidence: 99%

Gas Atomization of Amorphous Aluminum Powder: Part II. Experimental Investigation

Zheng

Lin

Zhou

et al. 2009

Metall Mater Trans B

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“…Most metallic glasses require very rapid quenching from the liquid state to retain their amorphous structure. Two recent advances are reported in the literature 135 . One advance is the discovery of a family of multicomponent alloys involving Zr, Fe and Mg based systems that can achieve the amorphous state in bulk volume at slow cooling rates or during intense deformation of a layered component assembly.…”

Section: Amorphous Metalsmentioning

confidence: 99%

Innovative forming and fabrication technologies : new opportunities.

Davis¹,

Hryn²

2008

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Executive SummaryThe state of technology in the field of fabrication and materials forming is reviewed. The purpose of this work is to identify new fields of Research & Development (R&D) that can lead to a significant reduction in energy consumption. This report, based on an extensive literature survey, identifies sheet aluminum alloy manufacturing, forming, and applications as a core aspect, but also highlights other types of sheet metal alloys and materials.This study found that aluminum alloy sheet manufacturing by the direct chill (DC) casting process is a mature technology where only marginal energy savings can be expected. Energy savings in this field can be accomplished mainly by individual plant wide assessments of energy consumption followed by optimization work. A possible breakthrough would come from advanced melting techniques such as plasma heating. As well, immersion heaters were recently identified as showing potential. An emerging technology in sheet manufacturing is spray rolling. The process could save 4.6x1012 kJ per year of energy for the U.S. aluminum industry. Even though the process has been proven to be technically feasible, the industrial implementation of spray rolling might need a significant effort. Improvements to the twin-roll casting process by coupling it with rheocasting could be an interesting method that would be easier to implement on the industrial scale.Extensive research has been performed to develop processes capable of forming commercial aluminum alloys for applications in the automotive industry. The following processes are considered advanced forming technologies: superplastic forming, electromagnetic forming, age forming, warm forming, and hydroforming. They are not necessarily new but can be regarded as emerging technologies with respect to their application to aluminum alloys. Superplastic forming is already being used industrially; however, simple and inexpensive manufacturing methods for the production of superplastic aluminum sheets still require further development. Any breakthrough in the forming of sheet materials will most likely come from the development of new alloys with very high formability at low temperature or the development of processing techniques to improve formability of existing alloys that will relax the stringent requirements of the forming techniques themselves. To have significant achievements in alloy development, thermodynamic models must be developed (or improved). The recent developments in quantum physics applied to aluminum alloys could pave the way for very efficient alloy development.Aluminum alloys are currently the material of choice to reduce weight in the automotive industry because of their commercial availability and the maturity of the aluminum industry. Opportunities still exist in the field of lightweight materials having high specific strength. Among those materials are magnesium alloys. Magnesium alloys could allow for further weight savings but high formability and high corrosion resistant alloys must be developed to overc...

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“…32) Indeed, based upon the comprehensive analysis developed by Inoue 1) it is clear that glass formation is favored for hypereutectic compositions. For the hypereutectic composition range, it is somewhat unexpected that the kinetic competition during crystallization would favor the Al solution phase as the primary reaction product.…”

Section: Phase Selection During Primary Crystallizationmentioning

confidence: 99%

Nanocrystallization Reactions in Amorphous Aluminum Alloys

et al. 2003

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Primary crystallization is the key reaction that controls the synthesis of nanostructured bulk volumes comprised of a high density (10 21 -10 23 m À3 ) of nanocrystals (7-20 nm) within an amorphous matrix. The primary crystallization kinetics in response to the annealing and the deformation of amorphous Al alloys are assessed in specific sample types and selected thermal treatments to evaluate primary nanocrystallization reactions. All amorphous Al alloy compositions are hypereutectic so that the initial phase selection of primary Al proceeds at a reduced driving free energy compared to thermodynamically favored intermetallic phases. Differential scanning calorimetry (DSC) studies on powders and melt spun ribbon (MSR) samples based upon thermal cycling and annealing below the glass transition, T g , demonstrate a strong sensitivity of the primary crystallization onset and reaction enthalpy to thermal history and the as-quenched state. Microcalorimetry investigations and careful analysis of nanocrystal size distributions for Al 92 Sm 8 MSRs following sub-T g anneals reveal a partial nanocrystallization reaction resulting from a transient, decaying nucleation rate and a limited supply of heterogeneous nucleation sites. While crystallization is generally thought of as a thermally activated process, it can also be induced in response to external forcing such as irradiation or mechanical alloying. Intense deformation of amorphous Al 88 Y 7 Fe 5 MSR, for example, yields a distribution of Al-nanocrystallites in the amorphous matrix without thermal annealing. Moreover, the results of cold-rolling experiments with melt-spun amorphous Al 85 Ni 10 Ce 5 ribbons show that the deformation process can alter the phase selection upon annealing. These results suggest that the shear process during rolling effects a local rearrangement of atoms in the amorphous matrix. The kinetics behavior highlights the important role of the as-synthesized amorphous structure, reaction pathways and transient conditions on the evolution of nanoscale microstructures during primary crystallization.

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Amorphous aluminum alloys—synthesis and stability

Cited by 85 publications

References 39 publications

Gas Atomization of Amorphous Aluminum Powder: Part II. Experimental Investigation

Gas Atomization of Amorphous Aluminum Powder: Part II. Experimental Investigation

Innovative forming and fabrication technologies : new opportunities.

Nanocrystallization Reactions in Amorphous Aluminum Alloys

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