Solid-State Phase Equilibria of the Mg-Gd-Nd System at 500 °C

Abstract

The phase equilibria at 500°C of the Mg-Gd-Nd system were investigated via a combination of a diffusion couple technique and the equilibrated alloys method, by means of the electron probe microanalyses and x-ray diffraction technique. It was revealed that continuous solid solutions of (Gd,Nd)Mg and (Gd,Nd)Mg 3 form between GdMg and NdMg and between GdMg 3 and NdMg 3 , respectively. No ternary compound was found. 3 three-phase equilibria, i.e. (Mg)+Nd 5 Mg 41 +GdMg 5 , Nd 5 Mg 41 +GdMg 5 +(Gd,Nd)Mg 3 and (Gd,Nd)Mg 3 +GdMg 2 +(Gd,Nd) Mg, were well determined. In addition, the homogeneity ranges of the binary phases in the MgGd and Mg-Nd systems were also well measured. The metastability of the NdMg l2 and GdMg 7 phases were confirmed and the isothermal section at 500°C was constructed in the present work.

Phase Equilibria at 500 °C of the Mg-Gd-La System

“…The GdMg 2 phase was not observed in all the diffusion couples though it is known as a stable compound at 500°C. This phase was observed by Das et al [6] in the binary Mg/Gd diffusion couple after 2 days' annealing at 470°C and also by the present authors [4] in one of the five Mg/(Gd,Nd) diffusion couples, i.e. Mg/Gd-8Nd, the one with the lowest Nd content in the Gd-Nd alloys.…”

“…Figure 5 is the isothermal section at 500°C of the MgGd-La system, which was constructed according to the present work and the experimental information on the binary systems in literature. [4,9,10] The three-phase equilibrium of GdMg 5 + La 2 Mg 17 + La 5 Mg 41 in the Mg-rich corner is shown with dashed lines since it was not well determined in the present work. The intermediate Sm-type (delta) phase in the Gd-La binary system, which was reported by Gschneidner and Calderwood, [10] was not detected in the present work.…”

“…The objective of the present work is to determine the isothermal section at 500°C of the MgGd-La system as one of our Mg-RE1-RE2 systems, [3,4] via a combination of the diffusion couple technique and equilibrated alloy method.…”

Phase Equilibria of the Mg-Gd-Ce System at 500 °C

“…Figure 4 presents the isothermal section at 500°C constructed according to the present work and literature data on the accepted binary systems. [8,9,14] The phase boundaries and three-phase equilibria, which were deduced or not well determined, are indicated with dashed lines. All the compositions below are in atomic percent unless otherwise stated.…”

“…[12] The present work is to determine the phase equilibria at 500°C of the Mg-Gd-Ce system within the framework of a longterm project for investigating the phase equilibria in the Mg-RE1-RE2 systems. [13][14][15] The temperature of 500°C is very near the solution heat treatment temperature for the aged Mg -Gd based alloys and there occurs no liquid phase at this temperature.…”