Critical Systematic Evaluation and Thermodynamic Optimization of the Fe-RE System: RE = Gd,Tb, Dy,Ho, Er,Tm, Lu,and Y

As the second part of the thermodynamic study of binary Fe-RE system, critical evaluations and optimizations of all available phase diagrams and thermodynamic data for the Fe-heavy RE (heavy RE = Gd, Tb, Dy, Ho, Er, Tm, Lu, and Y) systems were conducted to obtain reliable thermodynamic functions of all the phases in the systems. In the thermodynamic modeling of the heavy RE systems, systematic variations in the phase diagrams and thermodynamic properties such as the enthalpy of mixing in the liquid state and enthalpy of formation of solid compounds with the atomic number of lanthanide series were observed. These systematic trends were incorporated in the optimization of the Fe-heavy RE system to resolve inconsistencies between available experimental data and to estimate unknown thermodynamic properties. The systematic trends in thermodynamic properties of solid and liquid phases and phase diagram of the entire Fe-RE systems were summarized.     

Critical Systematic Evaluation and Thermodynamic Optimization of the Mn-RE System (RE = Tb,Dy, Ho,Er, Tm and Lu) with Key Experiments for the Mn-Dy System

Critical evaluation and optimization of all available phase diagrams and thermodynamic data for the Mn-RE (RE = Tb, Dy, Ho, Er, Tm, and Lu) systems has been conducted to obtain reliable thermodynamic functions of all the phases in the systems. Key experiments for the Mn-Dy system were performed using DSC and solution calorimeter. In the thermodynamic modeling, it is found that the Mn-RE systems show systematic changes in the phase diagrams and thermodynamic properties such as enthalpy of mixing in liquid state in the order of periodic number in the lanthanide series. The systematic thermodynamic modeling approach for RE elements allow to resolve inconsistencies in the experimental data and estimate unknown thermodynamic properties and phase equilibria of Mn-RE system.     

Effect of Si and Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Additions on the Oxidation Behavior of Ni–<Emphasis Type="Italic">x</Emphasis>Al (<Emphasis Type="Italic">x</Emphasis> = 5 or 10 wt%) Alloys at 1150 °C

The effect of Si and Y₂O₃ additions on the oxidation behavior of Ni–xAl (x = 5 or 10 wt%) alloys at 1150 °C was studied. The addition of Y₂O₃ accelerates oxidation rate of alloys, especially growth rate of NiO, but improves adherence of the scale to the substrate. The addition of Si facilitates the selective oxidation of Al, suppresses the formation of NiO and therefore reduces the critical Al content to form continuous layer of alumina scale. Higher Al content decreases the oxidation rate of alloys in binary Ni–Al alloys and increases the oxidation rate of alloys in ternary Ni–Al–Si alloys. The effect of third-element Si is more significant and beneficial than that of Al content in ternary Ni–Al–Si alloys.