Thermodynamic modeling of the Al–Mg–Na system

Zhang, Shengjun; Han, Qingyou; Liu, Zhe

doi:10.1016/j.jallcom.2005.10.002

Cited by 12 publications

(11 citation statements)

References 24 publications

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“…The experimental work and thermodynamic modeling of the Mg-Na system were carried out by several groups [ 81 – 85 ]. The main feature of Mg-Na system is the large immiscibility in the liquid phase.…”

Section: Literature Reviewmentioning

confidence: 99%

“…Lantratov [ 82 ] measured the activities of Na and Mg in the liquid along the complete composition range by EMF method at 973 K which exhibited strong positive deviation from ideality due to the limited solubility. In a recent study, Zhang et al [ 85 ] presented a thermodynamic model of the Mg-Na system as the constituent binary of the Al-Mg-Na ternary system. They [ 85 ] employed the random solution model for the liquid phase and calculated the Mg-Na phase diagram and the activities of Mg and Na in the liquid.…”

Section: Literature Reviewmentioning

confidence: 99%

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Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

Abdessameud

Mezbahul-Islam

Medraj

2014

The Scientific World Journal

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Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH 3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH 2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems.

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Section: Literature Reviewmentioning

confidence: 99%

Section: Literature Reviewmentioning

confidence: 99%

Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

Abdessameud

Mezbahul-Islam

Medraj

2014

The Scientific World Journal

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“…SEM was carried out on a Philips 525 FEGSEM with an energy dispersive Xray analysis (EDX) system in un-etched condition. The CALPHAD method was used to predict the phases developed in these alloys using the JMatPro software package (Saunders, 2001) for both equilibrium (Guo et al, 2005;Zhang, Han, & Liu, 2006;Lacaze & Valdes, 2005) and the non-equilibrium Scheil-Gulliver cooling condition (Ohno, Mirkovic, & Schmid-Fetzer, 2006;Quested, Dinsdale, & Greer, 2005). The hardness of the specimens was measured using a standard Rockwell Hardness testing machine in HRF scale with a 60 kg load and using a 1/16" diamond indenter.…”

Section: Methodsmentioning

confidence: 99%

Effects of Copper and Magnesium on Phase Formation Modeling and Mechanical Behavior in AL-CU-MG Alloys

Nafsin¹,

Rashed²

2013

Int J Automot Mech Eng

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The current work emphasizes the establishment of a relationship between microstructure, and copper and magnesium addition in aluminum based alloys. Aluminum alloys containing 4 and 6% copper and 0.50 and 1% magnesium were cast from commercially pure aluminum ingots and homogenized at 400 o C. Images of the microstructures of the as-cast and homogenized alloys were acquired, and image analysis of the phases was performed on the acquired images to obtain area fractions of the phases present in the microstructure. Using the CALPHAD modeling method, thermodynamic modeling of the alloys was carried out in the equilibrium cooling condition since after homogenization for a prolonged time the alloys should reach a close to equilibrium cooling condition. Phase fractions predicted in modeling were matched closely with image analysis data, given that phases present in the homogenized alloys can be interpreted through modeling in the equilibrium cooling condition. EDX analysis of the samples identified the phases present in the alloys as Al 2 Cu, Mg 2 Si and Al 7 Cu 2 Mg. With increasing copper content, it was found both in modeling and experimentally that the amount of Al 2 Cu phase increased, which improved the hardness values of the alloys. However, in the homogenized condition, the hardness values slightly decreased compared to those of the as-cast condition due to retention of a lower fraction of Al 2 Cu phase in the homogenized condition. This was ascertained in the modeling of the alloys. In contrast, Mg 2 Si and Al 7 Cu 2 Mg phases were formed when magnesium was added in the predefined amount; however, these phases were not found to be effective at improving the hardness of the alloys, and the hardness values were barely modified. Apparently, the hardness enhancement after magnesium addition occurred due to a solute effect. To observe the phase effect of magnesium in aluminum alloys, binary alloys of aluminum-magnesium should be cast.

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“…[10][11][12] In the CALPHAD thermodynamic modeling, the Gibbs energies of individual phase were modeled through the coupling of phase diagrams and thermochemistry, and the model parameters are collected in thermodynamic databases. Models for the Gibbs energy of binary and ternary phases are primarily based on the crystal structures of the phases.…”

Section: Phase Evolution and Comparison With Experimental Informationmentioning

confidence: 99%

“…The Gibbs energies of individual phases are expressed as a function of composition and temperature that can be used to reveal the phase relations and phase compositions. In the present study, Thermo-Calc [13] was used for free energy minimization and the Al-Li-Na-K database [10][11][12] was used for phase descriptions. Figure 1 shows the calculated isopleth section of Al-2.3Li-K (15 ppm)-Na alloys with respect to the Na content.…”

Section: Phase Evolution and Comparison With Experimental Informationmentioning

confidence: 99%

Thermodynamic Investigation of Alkali‐Metal‐Induced High Temperature Embrittlement in Al‐Li Alloys

2007

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Aluminum-lithium alloys are very important structural materials and widely used in aircraft and aerospace industries due to their contributions to higher fuel efficiency through weight reduction. Compared with other Al alloys, Al-Li alloys have a lower density at the equivalent strength levels. The addition of 1 wt. % Li to an Al alloy results in a 6 % increase in the elastic modulus and a 3 % decrease in density. However, they have a variable short-transverse fracture toughness in rolled, extruded and forged forms due to trace amounts of alkali-metal impurities like Na and K. Alkali-metal impurities are introduced into Al-Li alloys through feedback and pickup from refractories. Commercial grades Al-Li alloys usually contain 3-10 wt. ppm alkali-metal impurities inevitably.Payne and Eynon [1] first mentioned Na-induced embrittlement in Al-Li alloys for the Na content over 50 ppm. Vaynblat et al. [2,3] found that the fracture toughness drops 16 % in the Al-2Li-0.13Zr alloy if the Na content increases from 31 to 76 ppm. Vasudevan et al. [4] observed a linear decrease as a function of the Na content in the fracture toughness of Al-Li alloys containing up to 480 ppm Na. Webster [5] also found that toughness decreases in Al-Li alloys containing up to 434 ppm Na and 23 ppm K. Webster's further investigations [6,7] discovered particles enriched with Na, K, Cs and Rb on grain boundaries via transmission electron microscope (TEM) [6] as well as energy and wavelength dispersive analysis (EDX & WDX) and imaging secondary ion mass spectrometry (SIMS), [7] and suggested that they were liquid at high temperature due to their low melting temperature. Sweet et al. [8] studied the effects of alkali-metal impurities on the fracture toughness of Al-Li-Cu alloys extrusions and found brittle islands resulting from liquid-metal embrittlement due to the presence of discrete Na-and K-rich liquid phases in the grain boundaries.It has been found that alkali-metal-induced embrittlement in the Al-Li alloys occurs due to the formation of an intergranular alkali-metal-rich phase that significantly weakens the strength of grain boundaries by TEM, EDX, WDX and SIMS techniques. The performance of Al-Li alloys can be substantially improved via a vacuum refining process [7] and high-purity Al and Li pigs. However, these methods are rather costly. On the other hand, how to suppress alkali-metal-induced HTE by the means of controlling industrial processing parameters is still unknown and has not been explored. Fundamental understanding of Na-induced HTE in Al-Mg alloys has been provided via thermodynamic investigations by the authors successfully. [9] In the present work, efforts are made to understand the mechanism of alkali-metal-induced HTE in Al-Li alloys by revealing the correlations between HTE, phase formation, temperature, and composition through the thermodynamics of the Al-Li-Na-K quarternary system. Phase Evolution and Comparison with Experimental InformationThe thermodynamic database for the Al-Li-Na-K system has been developed by the pre...

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Thermodynamic modeling of the Al–Mg–Na system

Cited by 12 publications

References 24 publications

Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

Effects of Copper and Magnesium on Phase Formation Modeling and Mechanical Behavior in AL-CU-MG Alloys

Thermodynamic Investigation of Alkali‐Metal‐Induced High Temperature Embrittlement in Al‐Li Alloys

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