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Permanent Magnets

Thermo-Calc can be used to predict the thermodynamics and phase equilibria of neodymium, NdFeB-based alloys used for the production of permanent magnets.

Solutions for Permanent Magnetic Materials

Anisotropic bulk permanent magnets based on Nd-Fe-B alloys are the most widely used types of rare earth magnets, and their fabrication requires precise control of their microstructure. Two approaches to producing such magnets are (i) powder metallurgical sintering and (ii) rapid solidification followed by hot-deformation. In both cases, the resultant phase constitutions and morphology of the microstructure depend on the chemical compositions of the magnets and the processing conditions. Improved knowledge of the underlying thermodynamics and phase equilibria of these systems are important to improving the processing reliability and further development of Nd-Fe-B-based magnets.

Additionally, commercial Nd-Fe-B magnets are not just a simple ternary system, but rather exist as multicomponent alloys where additional elements such La, Ce, and Pr can be adopted to substitute for the more expensive Nd. Other elements may also be added to improve properties such as coercivity.

There is limited handbook data available for these multicomponent alloys, and those that exist do not always take into account variations in chemistry or processing conditions. Where this data is missing, Thermo-Calc can be used to generate the materials property data and make predictions of material behavior throughout the materials life cycle.

Calculate the following, based on your actual alloy chemistry:

  • Thermophysical properties, such as:
    • Specific heat, enthalpy, latent heat, and molar volume (for all phases), and the viscosity and surface tension (of liquid only)
    • Phase-based properties, such as:
      • Critical transformation temperatures such as solvus temperatures of precipitates, amounts and compositions of phases, solubility limits, activities, phase diagrams, and more
      • Equilibrium and non-equilibrium solidification, such as:
        • Liquidus, solidus, incipient melt temperatures, freezing range, fraction solid curves, solidification path, fraction eutectic, microsegregation, partition coefficients, latent heat, shrinkage, and more
        • Curie temperature

Application Examples

Thermo-Calc has many applications to NdFeB-based Permanent Magnets. Below is one such example.

Prediction of Curie Temperatures

The Curie temperature (Tc) is a critical temperature, above which certain materials lose their permanent magnetic properties. It is therefore one of the most important properties for permanent magnetic materials. As a result, developing new alloys that extend the temperature range of practical usage along with good structural stability is of strong interest.

The Curie temperature can be predicted using Thermo-Calc as a function of chemical composition. A comparison is made in the plot here against collected experimental data for a number of given industrial alloys.

A plot showing a comparison of calculated vs experimental Curie temperatures for several industrial allows.

Learn more about Applications to Permanent Magnetic Materials

A collection of examples that demonstrate the validity and calculation abilities of the TCPMAG database.

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