Metastable Iron-Rich Magnet Consolidation via Pulsed Current Sintering

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Solution Overview

Problem

There is a need for processes to prepare rare earth element-containing and iron-rich permanent magnet materials in particulate form that can be consolidated into densified bulk magnets without thermal degradation, retaining desirable magnetic properties.

Innovation Solution

The process involves spark plasma sintering (SPS) of small particles of metastable rare earth-iron compounds with a ThMn12 tetragonal crystal structure, using pulsed direct current to heat and compact the particles into dense bulk shapes at reduced temperatures, avoiding decomposition and preserving magnetic properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of stationary object

If conventional sintering or hot pressing is used to consolidate rare earth-iron compound particles, then densification can be achieved, but thermal degradation and decomposition of the metastable compound occurs

Engineering Contradiction:

Improvedensity of consolidated magnetVSAvoidstability of metastable compound

Core Design Contradiction:

Volume of stationary objectVSStability of the object's composition

Solution Approach 1:

The patent replaces conventional thermal field-based sintering methods with a pulsed electric current field (spark plasma sintering). This substitution allows rapid heating and consolidation that avoids the thermal degradation and decomposition issues associated with conventional sintering, while achieving the required densification of the metastable rare earth-iron compound particles

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent employs pulsed direct current rather than continuous heating. The periodic pulsing of electric current through the compacted particles enables rapid heating cycles that achieve densification before thermal degradation can occur, maintaining the metastable composition while achieving the desired density

Inventive Principle:

Principle #19Periodic action

2Volume of stationary object

If high temperature is applied to consolidate particles into dense bulk shapes, then densification is improved, but decomposition of the compound occurs

Engineering Contradiction:

Improvedensity of bulk magnetVSAvoiddecomposition of compound

Core Design Contradiction:

Volume of stationary objectVSObject-generated harmful factors

Solution Approach 1:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses rapid pulsed heating to quickly pass through the temperature range where decomposition would occur. The brief exposure to high temperatures during pulsed spark plasma sintering achieves densification while minimizing the time available for decomposition reactions, effectively 'rushing through' the harmful thermal exposure window

Inventive Principle:

Principle #21Skipping (Rushing through)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method effectively consolidates rare earth-iron compounds into dense bulk magnets with retained magnetic properties, achieving nearly full density and maintaining the original functional attributes of the material.

Implementation Method 1

a pulsed direct current (DC) is passed through the compacted particles to heat and sinter them into a densified shape

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

By using such a spark plasma sintering (SPS) technique and carefully selecting the processing parameters, powders, or like small particles, of metastable permanent magnet compound compositions can be consolidated into bulk shapes

Methodology Applied

Scientific EffectSpark plasma sintering: Spark Plasma Sintering

Data Source

PatentUS10930417B2Rapid consolidation method for preparing bulk metastable iron-rich materials

Publication Date: 2021.02.23 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

Interstitially modified compounds of rare earth element-containing, iron-rich compounds may be synthesized with a ThMn12 tetragonal crystal structure such that the compounds have useful permanent magnet properties. It is difficult to consolidate particles of the compounds into a bulk shape without altering the composition and magnetic properties of the metastable material. A combination of thermal analysis and crystal structure analysis of each compound may be used to establish heating and consolidation parameters for sintering of the particles into useful magnet shapes.