Bulk Anisotropic Exchange-Spring Magnets Reducing Rare Earth Content
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Solution Overview
Problem
Current bulk permanent magnet nanocomposites rely heavily on rare earth elements, which are scarce and costly, and face challenges in achieving high coercivity and energy product values due to limitations in grain alignment and intergranular coupling.
Innovation Solution
A method involving melting a precursor alloy with a hard magnetic phase and a magnetically soft phase, followed by casting into flakes, milling into powder, and pressure crystallization to promote crystal growth and achieve uniform distribution and alignment, reducing rare earth content while maintaining or improving magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rare earth elements are used to achieve high coercivity and energy product values, then magnetic performance is improved, but material cost and scarcity issues worsen
Solution Approach 1:
The patent changes the compositional parameters by reducing rare earth content from conventional levels to below stoichiometric amounts (e.g., Nd content reduced from 11.76 at.% to 5.9-8.2 at.%), while adjusting transition metal ratios to maintain magnetic performance through parameter optimization
Solution Approach 2:
The patent creates a composite nanocomposite structure with hard magnetic phase (Nd2Fe14B) and soft magnetic phase (α-Fe) distributed at nanometer scale, where the composite structure compensates for reduced rare earth content by leveraging exchange-spring effects between phases
2Reliability
If grain alignment is achieved to improve coercivity, then magnetic anisotropy is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by aligning magnetic grains during the solidification and hot deformation processes before final magnet fabrication, using external magnetic fields and mechanical deformation to establish preferred orientation that is then locked in during subsequent processing
Solution Approach 2:
The patent replaces conventional mechanical alignment methods with a combination of magnetic field application during solidification and thermomechanical processing, where magnetic fields induce preferred grain orientation without requiring complex mechanical alignment equipment
3Power
If nanocomposite structure is created to improve exchange-spring effect, then energy product is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes phase transitions during controlled solidification and heat treatment processes to naturally separate and distribute hard and soft magnetic phases at appropriate nanometer scale distances, leveraging thermodynamic phase separation to achieve uniform distribution without requiring ultra-precise manufacturing control
Solution Approach 2:
The patent introduces an intermediary amorphous phase or liquid phase during processing that facilitates uniform mixing and distribution of hard and soft magnetic components before final solidification, acting as a mediator that enables nanocomposite formation with reduced manufacturing precision requirements
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
The method results in permanent magnets with enhanced coercivity and energy product values, achieving full intergranular coupling and anisotropic behavior with reduced rare earth content, comparable to conventional systems, and allows for tailored grain sizes for optimal performance.
Implementation Method 1
PM nanocomposites are generally comprised of a hard magnetic phase and a magnetically soft phase, which benefit from the spring-exchange effect whereby a high saturation magnetization of the magnetically soft phase and a large coercivity of the hard magnetic phase results
Implementation Method 2
to obtain large Hc values, a strong uniaxial magnetocrystalline anisotropy (Ku) is required (that is, the hard magnetic phase should be aligned)
Implementation Method 3
pressure crystallization to promote crystal growth and achieve uniform distribution and alignment
Data Source
AI summary
A method of preparing a permanent magnet nanocomposite. The method includes melting a precursor alloy having a hard magnetic phase and a magnetically soft phase. The hard magnetic phase has less than a stoichiometric amount of rare earth metal or noble metal. The melted precursor is cast into flakes and milled into a powder. The powder may then be pressure crystalized.