Grain Boundary Diffusion in Rare-Earth Magnets

Solution Overview

Problem

The high cost of rare-earth magnets, particularly those containing heavy rare-earth elements, limits their widespread use due to the expense of these elements, and existing methods for reducing their content, such as grain boundary diffusion, are limited in thickness and mechanical properties.

Innovation Solution

A process involving the sintering of rare-earth magnets with alternating layers of heavy rare-earth elements and magnetic powder, allowing for a concentration profile that enhances coercivity and anti-demagnetizing properties while reducing the overall amount of heavy rare-earth elements used, enabling the production of thicker magnets with improved mechanical properties and cost-effectiveness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If heavy rare-earth elements are added to ensure high-temperature operation, then coercivity and anti-demagnetizing ability are improved, but manufacturing cost increases significantly

Engineering Contradiction:

ImprovecoercivityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies local quality by creating alternating layers with different HRE concentrations within the magnet structure. Some regions have high HRE content for maximum coercivity, while other regions have lower HRE content to reduce overall cost. This spatial variation in material composition allows the magnet to achieve required performance with reduced total HRE usage.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the concentration parameter of HRE elements by creating a periodic concentration profile instead of uniform distribution. By varying the HRE concentration across different layers and controlling diffusion during sintering, the magnet achieves optimized coercivity at reduced material cost.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If grain boundary diffusion is used to reduce heavy rare-earth content, then manufacturing cost decreases, but magnet thickness is limited and mechanical properties deteriorate

Engineering Contradiction:

Improvemanufacturing costVSAvoidmagnet thickness

Core Design Contradiction:

Ease of manufactureVSLength of moving object

Solution Approach 1:

The patent segments the magnet into alternating layers of different compositions during the sintering process. By introducing HRE-containing layers at specific positions and controlling their diffusion, the method creates a periodic concentration profile that maintains coercivity throughout the bulk, enabling production of thicker magnets with improved mechanical properties.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies preliminary action by pre-positioning HRE-containing layers within the green compact before sintering. This allows controlled diffusion during the sintering process to create the desired concentration profile, enabling production of thicker magnets with improved mechanical properties while maintaining cost-effectiveness.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If heavy rare-earth elements are added to ensure high-temperature operation, then anti-demagnetizing ability is improved, but the overall amount of expensive material increases

Engineering Contradiction:

Improveanti-demagnetizing abilityVSAvoidamount of heavy rare-earth elements

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by creating alternating layers with different HRE concentrations within the magnet structure. Some regions have high HRE content for maximum coercivity, while other regions have lower HRE content to reduce overall cost. This spatial variation in material composition allows the magnet to achieve required performance with reduced total HRE usage.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the concentration parameter of HRE elements by creating a periodic concentration profile instead of uniform distribution. By varying the HRE concentration across different layers and controlling diffusion during sintering, the magnet achieves optimized coercivity at reduced material cost.

Inventive Principle:

Principle #35Parameter changes

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 enables the production of rare-earth magnets with enhanced coercivity and anti-demagnetizing properties across a wider range of thicknesses, reducing the need for expensive heavy rare-earth elements and improving mechanical strength, while also allowing for tunable magnetic profiles and reduced eddy current losses.

Implementation Method 1

HRE elements diffused into a rare-earth element bulk

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

sintering the green compact to form a rare-earth magnet

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS10290407B2Grain boundary diffusion process for rare-earth magnets

Publication Date: 2019.05.14 FORD GLOBAL TECH LLC

AI summary

In at least one embodiment, a single sintered magnet is provided having a concentration profile of heavy rare-earth (HRE) elements within a continuously sintered rare-earth (RE) magnet bulk. The concentration profile may include at least one local maximum of HRE element concentration within the bulk such that a coercivity profile of the magnet has at least one local maximum within the bulk. The magnet may be formed by introducing alternating layers of an HRE containing material and a magnetic powder into a mold, pressing the layers into a green compact, and sintering the green compact to form a single, unitary magnet.