Thermodynamic studies and the phase diagram of the Li-Mg system

Gąsior, W.; Moser, Z.; Zakulski, W.; Schwitzgebel, G.

doi:10.1007/bf02652335

Cited by 62 publications

(38 citation statements)

References 14 publications

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“…% results in total conversion. 5 Although the Mg-Li system has been studied extensively, [5][6][7][8][9][10][11] evidence suggesting the formation of ordered phases is notably sparse. Diffusionless transformations of the martensitic type have been observed in pure Li, and similar transformations occur in low-temperature magnesium alloyed lithium at certain concentrations.…”

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confidence: 99%

Ordered magnesium-lithium alloys: First-principles predictions

2010

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Magnesium-lithium ͑Mg-Li͒ alloys are among the lightest structural materials. Although considerable work has been done on the Mg-Li system, little is known regarding potential ordered phases. A first and rapid analysis of the system with the high-throughput method reveals an unexpected wealth of potentially stable low-temperature phases. Subsequent cluster expansions constructed for bcc and hcp superstructures extend the analysis and verify our high-throughput results. Of particular interest are those structures with greater than 13 at. % lithium, as they exhibit either partial or complete formation as a cubic structure. Order-disorder transition temperatures are predicted by Monte Carlo simulations to be in the range 200-500 K. I. MOTIVATION AND BACKGROUNDEmerging technologies increasingly depend on the production of ultralight-weight materials. Magnesium-lithium ͑Mg-Li͒ alloys are the lightest metallic alloys, having densities near that of plastics, 1-3 and are strong enough to be used in a variety of high-performance applications. In particular, Mg-Li alloys are good candidates for material applications in industries such as aerospace and automotive manufacturing. 4 As an alloying agent in magnesium, lithium is advantageous principally because of its low density and cubic crystal structure. The addition of lithium converts the hexagonalclose-packed ͑hcp͒ structure of natural magnesium to a more ductile and formable body-centered-cubic ͑bcc͒ alloy. Addition of 13 at. % Li partially converts the alloy to a cubic structure and content exceeding 33 at. % results in total conversion. 5 Although the Mg-Li system has been studied extensively, 5-11 evidence suggesting the formation of ordered phases is notably sparse. Diffusionless transformations of the martensitic type have been observed in pure Li, and similar transformations occur in low-temperature magnesium alloyed lithium at certain concentrations. 11,12 Binary ordered phases have not been conclusively identified, however, and any instances contained in the literature are indeterminate. 6,9,13,14 The results of high-throughput ͑HT͒ ab initio calculations performed with the AFLOW package ͑described later͒ show, however, that the heat of formation is negative for a large number of potential structure types, implying the existence of at least one thermodynamically stable ordered phase ͑Fig. 1͒. II. FIRST-PRINCIPLES METHODFollowing the HT results, we have made predictions of Mg-Li ordered phases using the cluster-expansion ͑CE͒ method-a first-principles-based approach in which input data is mapped to a truncated Ising-type Hamiltonian. The configurational Hamiltonian allows for a fast ground-state search ͑GSS͒ over many derivative superstructures. 16 The CE method was applied to the Mg and Li lattice configurations ͑bcc and hcp, respectively͒. Although minimum-energy configurations may exist outside those considered, superstructures derived from the parent lattices of the alloy constituents generally include the lowest-energy configurations. This assumption is ...

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confidence: 99%

Ordered magnesium-lithium alloys: First-principles predictions

2010

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“…It has been reported that the addition of Li element could decrease the c/a ratio of hexagonal Mg lattice and even change the crystalline structure of Mg alloys [1]. When Li content exceeds 5.3 wt.%, a Li-based body-centered-cubic (BCC, ␤ phase) structure will be introduced to hexagonal magnesium, which results in (␣ + ␤) duplex phases in Mg-Li-based alloys [2].…”

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Effect of Y on microstructure and mechanical properties of duplex Mg–7Li alloys

Dong

Wang

2010

Journal of Alloys and Compounds

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“…[1,2] When the lithium content exceeds 5 wt pct, the hexagonal magnesium will be partly transformed into body-centeredcubic (bcc) structure, while the structure of magnesium alloys will fully be converted from the hcp lattice to the bcc when lithium content is over 11 wt pct. [3] Consequently, the plasticity of the magnesium-lithium alloys is improved. Magnesium-lithium alloys are also regarded as the lightest metallic structural material.…”

Section: Introductionmentioning

confidence: 99%

Electrolytic Deposition and Diffusion of Lithium onto Magnesium-9 Wt Pct Yttrium Bulk Alloy in Low-Temperature Molten Salt of Lithium Chloride and Potassium Chloride

Dong

Wang

2009

Metall Mater Trans B

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The electrolytic deposition and diffusion of lithium onto bulk magnesium-9 wt pct yttrium alloy cathode in molten salt of 47 wt pct lithium chloride and 53 wt pct potassium chloride at 693 K were investigated. Results show that magnesium-yttrium-lithium ternary alloys are formed on the surface of the cathodes, and a penetration depth of 642 lm is acquired after 2 hours of electrolysis at the cathodic current density of 0.06 AAEcm À2 . The diffusion of lithium results in a great amount of precipitates in the lithium containing layer. These precipitates are the compound of Mg 41 Y 5 , which arrange along the grain boundaries and hinder the diffusion of lithium, and solid solution of yttrium in magnesium. The grain boundaries and the twins of the magnesium-9 wt pct yttrium substrate also have negative effects on the diffusion of lithium.

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Thermodynamic studies and the phase diagram of the Li-Mg system

Cited by 62 publications

References 14 publications

Ordered magnesium-lithium alloys: First-principles predictions

Ordered magnesium-lithium alloys: First-principles predictions

Effect of Y on microstructure and mechanical properties of duplex Mg–7Li alloys

Electrolytic Deposition and Diffusion of Lithium onto Magnesium-9 Wt Pct Yttrium Bulk Alloy in Low-Temperature Molten Salt of Lithium Chloride and Potassium Chloride

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