Grain Boundary Engineering for Nd-Fe-B Magnets
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Solution Overview
Problem
The global market for Rare Earth Permanent Magnets (REPMs) faces challenges due to the scarcity of Dysprosium (Dy), which limits the production of high-temperature performance Nd—Fe—B magnets, essential for energy-saving motor applications, leading to supply risks and increased costs.
Innovation Solution
The Grain Boundary Engineering (GBE) process reduces Dy content in Nd—Fe—B magnets by modifying the grain boundary phase while maintaining the original grain phase, allowing for the creation of magnets with improved temperature resistance and lower production costs, using a method that includes melting magnetic elements, forming cast alloy flakes, pulverizing, pressing, aligning, sintering, and mixing with rare earth and elemental additives to produce a homogeneous powder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If Dysprosium (Dy) content is increased to improve temperature resistance, then high-temperature performance is improved, but production cost increases and supply risk increases due to scarcity
Solution Approach 1:
The patent applies local quality by modifying only the grain boundary phase composition rather than the entire magnet. By adding Dy selectively to the grain boundary region (creating a Nd-Dy-B rich phase) while keeping the grain interior composition unchanged, the patent achieves localized temperature resistance improvement at lower overall Dy content, thus reducing production cost while maintaining high-temperature performance.
2Temperature
If Dysprosium (Dy) content is increased to improve temperature resistance, then high-temperature performance is improved, but Dy supply risk increases due to scarcity
Solution Approach 1:
The patent concentrates Dy in the grain boundary region rather than distributing it uniformly throughout the magnet. This localized enrichment creates a protective Nd-Dy-B rich phase at the grain boundaries that provides temperature resistance with minimal overall Dy content, thus reducing supply risk while achieving the desired temperature performance.
Solution Approach 2:
The patent creates a composite microstructure consisting of Nd-Fe-B grain interior phase and Nd-Dy-B grain boundary rich phase. This composite structure allows the magnet to achieve high-temperature performance through the Dy-containing grain boundary phase while maintaining low overall Dy content, as the bulk of the magnet volume consists of Dy-free or low-Dy grain interiors.
3Ease of manufacture
If Grain Boundary Engineering is applied to reduce Dy content, then production cost is reduced, but manufacturing process complexity increases
Solution Approach 1:
The patent applies preliminary action by adding Dy to the molten alloy before solidification, allowing the Dy to automatically segregate to the grain boundary regions during the casting process. This preliminary addition eliminates the need for subsequent complex post-processing steps to create the grain boundary rich phase, thus reducing manufacturing process complexity while achieving the desired grain boundary composition.
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
GBE achieves high-temperature performance and cost reduction by maintaining at least 90% of the original Nd—Fe—B 2:14:1 phase grains, replacing the Nd-rich grain boundary phase with a new phase made from additive materials, resulting in magnets with enhanced coercivity and remanence, and improved corrosion resistance, while minimizing Dy usage.
Implementation Method 1
mixing the second powder with a) a rare earth material R and b) an elemental additive A to produce a homogeneous powder
Implementation Method 2
sintering and magnetizing the homogeneous powder to form an Nd—Fe—B magnetic product
Implementation Method 3
sintering and magnetizing the homogeneous powder to form an Nd—Fe—B magnetic product
Data Source
AI summary
This disclosure is directed to sintered bodies comprising grains and a grain boundary composition, wherein: (a) the grains comprise a composition substantially represented by a formula G2M14B, where G is Nd, Dy, Pr, Tb, or a combination thereof, and M is Co, Fe, Ni, or a combination thereof, wherein the grains are optionally doped with one or more rare earth elements; and (b) the grain boundary composition is an alloy composition substantially represented by the formula: Nd8.5-12.5Dy35-45Co32-41Cu3-6.5Fe1.5-5, wherein the subscript values are atom percent relative to the total composition of the the alloy composition. Corresponding populations of particles are also disclosed