Author: Ahmad_2

Experimental Investigation and Thermodynamic Modeling of Mg-{Mn, Zn}-{Ce, Nd} Ternary system
Ahmad Mostafa1, Pampa Ghosh1 , Arthur Pelton2 and Mamoun Medraj1
1Concordia University, 2 Ecole Polytechnique

Introduction
In recent development of Mg-based alloys, Ce and Nd are now added to increase the high temperature strength. As part of the MagNET project, attempts are being made to develop a comprehensive database for the Mg-{Mn, Zn}-{Ce, Nd} systems using both thermodynamic modeling and experimental investigations.

Methodology

Key
samples

Data Verification

DSC

Experimental
Investigation

Literature Data

Thermodynamic
Modeling

Software

XRD

EPMA

Data

Diffusion
Couples
samples

Thermodynamic Database

The data available in the literature are contradictory and reflects the experimental difficulties encountered during investigation of the Mn-Nd system.

Mn-Nd Binary Phase Diagram

Nd

Line Scan

Mn

Mn2Nd

Mn23Nd6

Solid/Solid diffusion couple from 100%Nd to 100% Mn annealed at 650°C for 4 weeks.

Diffusion couples:
The diffusion couples were prepared under argon environment to avoid the oxidation of the two end members.
The Mn grinded disk was squeezed between two Nd grinded disks in a form of sandwich.
Then, the produced diffusion couples were wrapped in Ta foil and placed inside the quartz tube.

Mn2Nd

Mn23Nd6

Heating and cooling curves of the 27.8at%Mn (Eutectic composition) sample.

Microstructure of 64.23 at% Mn containing sample annealed at 650°C for 4 weeks.

Schematic Mn-Nd binary phase diagram (Saccone, 1993) showing the prepared key sample compositions, and the DSC heating and cooling signals.

Intensity

Mn2Nd 28.9%

Mn 71.1%

X-Ray Diffraction:
The annealed samples were crushed into powder shape under vacuum to prepare for the XRD examination.
The phases have been identified and compared with the phase diagram.

Diffusion couples and key samples were inserted into quartz tube under vacuum to be annealed at certain temperature.

2°θ

XRD Pattern of the 92.4at%Mn at room temperature

Ce-Mg-Mn ternary system:
Cerium-Magnesium-Manganese system is considered a promising new Mg alloy for many industrial applications such as automotive and aerospace. Alloys from this system exhibit a promising creep performance at elevated temperatures .

Thermodynamic Modeling:
System optimization is carried out using the Factsage software. The Ce-Mg-Mn ternary system is extrapolated from the constituent binary models.
Besides, all the other relevant experimental data are taken into account during modeling of this system.

Differential Scanning Calorimetry (DSC) :
60 mg samples were cut to fit into the alumina crucible.
The heating and cooling rates ranged from 5°C/min up to 10°C/min.
The phases transformation were detected as shown in the Mn-Nd phase diagram.
The Mn-Nd eutectic temperature was detected at 684°C±5.50.