Experimental investigation and thermodynamic assessment of the Mg–Gd–Ag system focused on Mg-rich region

Chen, Xinyu; Zhang, Yu; Peng, Liming; Zhang, Chuan

doi:10.1016/j.calphad.2014.10.002

Cited by 14 publications

(6 citation statements)

References 43 publications

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“…The composition of this phase is estimated by EDS in SEM, as marked by the red arrow in Figure 2 a. This indicates that the ratio of Mg and RE in the phase is around 17:3, which is similar to the one in Mg-Gg-Ag alloys reported in [ 30 ]. After solid solution, most of the Mg 17 RE 3 phase dissolves into the matrix, while the Mg 5 Gd phase remains in grain boundaries.…”

Section: Resultssupporting

confidence: 75%

Grain Refinement and Aging Hardening of the Mg-10Gd-3Y-2Ag-0.4Zr Alloy Produced by a Two-Step Forming Process

Ning

Gao

et al. 2018

Materials

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Grain refinement and precipitation are two effective ways to improve the mechanical properties of Mg-RE alloys. In this work, a two-step forming process is proposed. This includes cold rolling and subsequent annealing at high temperature for a short duration. By the two-step forming process, grains can be refined from 100 μm to 20 μm in compare with ~30 μm by common hot rolling at 450 °C for a reduction of 80%. The sample shows more distinct aging hardening, as the hardness amplification of 60 HV is twice that of the hot-rolled sample. The precipitation is observed by high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). Dynamic precipitation in the sample by the two-step route is found to be effectively suppressed. Interestingly, after subsequent annealing, the density of precipitation, especially β′, become much higher than that in hot-rolled samples.

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Section: Resultssupporting

confidence: 75%

Grain Refinement and Aging Hardening of the Mg-10Gd-3Y-2Ag-0.4Zr Alloy Produced by a Two-Step Forming Process

Ning

Gao

et al. 2018

Materials

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Section: Resultsmentioning

confidence: 86%

“…A major difference to the phase equilibria in the Mg-Gd-Ag system reported by Chen et al [42] is that their ternary phase X is given as having a diamond cubic structure (similar to the structure of the equilibrium intermetallic phase in Mg-Y-Ag alloys [23])⎯instead of orthorhombic⎯even though its composition is approximately GdAgMg11, similar to NdAgMg11. A narrow stoichiometric range for X in a sub-lattice model (Ag, Gd)0.15(Mg)0.85 was reported, the stable composition at 673 and 723 K (400 and 450 °C) measured by EPMA is near Gd7.5Ag7.5Mg85 [42]. Present calculations using the thermodynamic Mg-Gd-Ag database [42] reveal that the X phase may also form as the first intermetallic phase during solidification of Mg-rich alloys in a mono-variant eutectic reaction, Liquid → Hcp + X. Scheil solidification calculations were also performed, revealing that the range of RE/Ag weight ratios in the alloy resulting in the eutectic reaction differ significantly for Gd or Nd.…”

Section: Resultsmentioning

confidence: 86%

“…The equilibrium intermetallic phase in the QE22 alloy was reported to be Mg12Nd2Ag with a complex hexagonal structure [25], or (Mg, Ag)12Nd with a Mg12Nd structure (I4/mmm, a = 1.031 nm, c = 0.593 nm) [15,[26][27][28][29]. The (Mg, Ag)12Nd was proposed [26,27] Zn-Zr alloy [23], the ternary intermetallic phase in a Mg-Gd-Ag alloy [42], and the ternary equilibrium precipitate phase in a Mg-Gd-Ag-Zr alloy [19], they were all reported to have a diamond-cubic structure (space group Fd3 ̅ m, a = 1.59 nm). in which the two Ag atoms in each column were arranged to be next to each other in the column, was also examined, and it showed that the energy was increased.…”

Section: Resultsmentioning

confidence: 99%

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On the Equilibrium Intermetallic Phase in Mg-Nd-Ag Alloys

Zhao

Chen

et al. 2019

Metall Mater Trans A

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The equilibrium intermetallic phase in Mg-Nd-Ag alloys has not been well understood. In this work, intermetallic particles in the solution-treated microstructure of commercial magnesium alloy QE22 (Mg-2.5Ag-2.0Nd-0.7Zr, wt pct) have been investigated using scanning electron microscopy, electron diffraction, atomic-resolution imaging and mapping techniques of scanning transmission electron microscopy (STEM) and thermodynamic modelling. The intermetallic particles are distributed in the inter-dendritic regions. They have coarse irregular shape and share the same crystal structure. The intermetallic phase (designated δ) is determined to have an orthorhombic structure (space group Cmcm, a = 1.02 nm, b = 1.18 nm, c = 1.00 nm) and a composition of NdAgMg11, which are different from those reported previously. An atomic model is proposed for the δ phase based on atomicresolution STEM images and atomic-scale energy-dispersive X-ray spectroscopy maps. The δ lattice is structurally related to that of Mg12Nd phase in binary Mg-Nd alloys. The Gibbs energy of formation of NdAgMg11 is determined from the equilibrium study at 793 K (520 °C), including the entropy of formation using the present experimental phase analysis data obtained at lower temperature.Implications to the formation temperature range and thermal stability of this phase and alloy solidification are discussed based on the calculated Mg-Nd-Ag phase diagram and Scheil solidification paths of alloys.

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“…The general equation of the molar Gibbs energy for solution phases such as liquid (L) and disordered solid solutions in a ternary system is based on a substitutional solution model, expressed as follows [21,22] :

…”

Section: Methodsmentioning

confidence: 99%

Sn–Ag–Cu nanosolders: Melting behavior and phase diagram prediction in the Sn-rich corner of the ternary system

Roshanghias

Vřešťál

Yakymovych

et al. 2015

Calphad

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Melting temperatures of Sn–Ag–Cu (SAC) alloys in the Sn-rich corner are of interest for lead-free soldering. At the same time, nanoparticle solders with depressed melting temperatures close to the Sn–Pb eutectic temperature have received increasing attention. Recently, the phase stability of nanoparticles has been the subject of plenty of theoretical and empirical investigations. In the present study, SAC nanoparticles of various sizes have been synthesized via chemical reduction and the size dependent melting point depression of these particles has been specified experimentally. The liquidus projection in the Sn-rich corner of the ternary SAC system has also been calculated as a function of particle size, based on the CALPHAD-approach. The calculated melting temperatures were compared with those obtained experimentally and with values reported in the literature, which revealed good agreement. The model also predicts that with decreasing particle size, the eutectic composition shifts towards the Sn-rich corner.

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Experimental investigation and thermodynamic assessment of the Mg–Gd–Ag system focused on Mg-rich region

Cited by 14 publications

References 43 publications

Grain Refinement and Aging Hardening of the Mg-10Gd-3Y-2Ag-0.4Zr Alloy Produced by a Two-Step Forming Process

Grain Refinement and Aging Hardening of the Mg-10Gd-3Y-2Ag-0.4Zr Alloy Produced by a Two-Step Forming Process

On the Equilibrium Intermetallic Phase in Mg-Nd-Ag Alloys

Sn–Ag–Cu nanosolders: Melting behavior and phase diagram prediction in the Sn-rich corner of the ternary system

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