Thermodynamic Assessment Of Mg Research Articles

Thermodynamic description of Mg–Zn–Sb system supported by experimental work and extrapolation to the Mg–Zn–Al–Sb quaternary system

Magnesium-zinc-antimony (Mg–Zn–Sb) system is a promising cast Mg alloy system. Herein, the thermodynamic assessment of Mg–Zn–Sb ternary system was carried out using the CALculation of PHAse Diagram (CALPHAD) approach coupled with the experimental data in this work. The transformation temperatures and the isothermal section of the Mg-rich corner at 300 °C was investigated. Afterwards, a set of self-consistent parameters of Mg–Zn–Sb system were achieved combined with the thermodynamic descriptions of Mg–Sb and Mg–Zn systems as well as the updated description of Zn–Sb system in the present work. Meanwhile, the ternary Al–Zn–Sb system was re-assessed based on the available literature data. A set of reliable parameters describing the ternary Al–Zn–Sb system were obtained, and the present calculated results can reproduce most of the phase equilibria data. The thermodynamic description of Mg–Al–Zn–Sb systems was then developed using the extrapolation method from the descriptions of the constituent sub-ternary systems.

A thermodynamic assessment of the Mg–Sn–Sb ternary system

Magnesium-tin-antimony (Mg–Sn–Sb) system is a promising system for developing high-creep resistance magnesium alloy and the alloy-type anode of magnesium recharge battery. Herein, the thermodynamic assessment of Mg–Sn–Sb ternary system was carried out using the CALculaiton of PHAse Diagram (CALPHAD) approach based on available literature data. The liquid phase was described via the associated model with associates Mg3Sb2 and Mg2Sn, and the compounds were described using the sublattice model. The consistency of the calculated phase equilibria relations and thermochemical properties with the available experimental data of Mg–Sn–Sb ternary system is presented. The thermodynamic descriptions of Mg–Sb, Sn–Sb binary systems and Mg–Sn–Sb ternary system assessed in this work provide a thermodynamic basis for the alloy design of magnesium alloy.

Thermodynamic assessment of Mg−Ni−Y system focusing on long-period stacking ordered phases in the Mg-rich corner

• The phase equilibria around LPSOs in Mg-Ni-Y system are experimentally determined. • The thermodynamic stability of LPSOs is discussed based on DFT calculations. • A distort 12R structure is observed through SEAD and HRTEM. • The phase diagram of Mg-Ni-Y system is optimized considering the new 12R LPSO. The long-period stacking ordered phases (LPSOs) in Mg−Ni−Y system have been attracting great interest as effective strengthening components because of their unique structural characteristics and deformation mechanism. However, the phase relationships in LPSOs are complicated and unclear, which restricts the design of advanced magnesium-based alloys. The aim of the present work is to experimentally determine the phase equilibria relationships focusing on LPSOs and establish the thermodynamic description for Mg−Ni−Y system. Four types of LPSOs, that is, 14H, 12R, 18R and 10H, are confirmed through equilibrated alloys and high-resolution transmission electron microscopy (HR-TEM). The formation enthalpies of LPSOs (14H, 12R, 18R and 10H) are calculated based on density functional theories (DFT) calculations. A new ternary compound, termed as τ phase, is observed for the first time which is likely to be the distorted structure of 12R as determined from the TEM image which shows a 12-layer closed packing plane distance of 3.252 nm and a shear angle of 83.2° between (0002) and (10 1 ¯ 0) planes. Based on the determined phase equilibria relationship, the Mg−Ni−Y system is assessed and a self-consistent description is obtained where the LPSOs are modeled as the stoichiometric compounds. The comparison between the calculation result and experimental data suggests the accuracy of the present thermodynamic database in the Mg-rich corner.

Thermodynamic assessment of Mg–Al–Mn phase equilibria, focusing on Mg-rich alloys

Abstract A thermodynamic description of the Mg–Al–Mn system on the basis of critically assessed experimental data is presented. Particular attention is placed on the solubility of manganese in Mg-rich liquid alloys. The overall consistency between calculated and experimental phase equilibria is shown and the Calphad assessment enables a clear identification of consistency of various groups of data. In manganese-saturated liquid alloys the primary crystallizing phases are β-Mn and Al8Mn5 up to 23 wt.% Al and below 815 °C. Two invariant reactions, ∊(hcp)↔ L + β-Mn + Al8Mn5 (815 °C) and L + β-Mn↔Mg(hcp) + Al8Mn5 (637 °C) occur in Mg-rich liquid alloys. In addition, the solidus temperature and solid phase equilibria are given by the present thermodynamic calculation.