Anisotropic Rare-Earth Bulk Magnet with Controlled ReFe2 Phase
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Solution Overview
Problem
The challenge in manufacturing anisotropic rare-earth bulk magnets is the formation of ReFe2 phase, which reduces magnetic properties due to its high Curie Temperature and paramagnetic properties at room temperature, leading to decreased remanent magnetization and orientation of crystal grains.
Innovation Solution
A method involving the preparation of amorphous magnetic powders containing Nd and Ce, followed by press-sintering and hot-deforming to control the weight fraction of ReFe2 phase, ensuring it satisfies P≤A*X−3, where P is the weight fraction of ReFe2 phase, X is the mole fraction of Ce, and A is 13 to 15, resulting in small-sized crystal grains with controlled alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ce is added instead of Nd to reduce cost, then manufacturing cost is reduced, but ReFe2 phase is generated which decreases magnetic properties
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Ce content within 3-10 atomic percent and adjusting the composition ratios of Nd, Fe, and B. By changing these compositional parameters, the patent suppresses ReFe2 phase generation while maintaining cost benefits from Ce addition. The specific parameter range for Ce content is critical to resolving the contradiction between cost reduction and magnetic property maintenance.
Solution Approach 2:
The patent uses composite material design by creating a multi-phase structure consisting of Re2Fe14B main phase, Nd-rich phase at grain boundaries, and controlled ReFe2 phase. This composite approach allows the material to benefit from Ce addition for cost reduction while maintaining magnetic properties through the synergistic combination of different phases with complementary functions.
2Ease of manufacture
If ReFe2 phase is generated during manufacturing, then manufacturing process is simplified, but remanent magnetization and crystal grain orientation are decreased
Solution Approach 1:
The patent applies parameter changes by optimizing the hot-deforming temperature range (400-600°C) and pressure conditions to control crystal grain orientation without promoting excessive ReFe2 phase formation. By precisely controlling these processing parameters, the patent achieves both ease of manufacture and high manufacturing precision in terms of crystal grain alignment.
Solution Approach 2:
The patent applies preliminary action by conducting press-sintering before hot-deforming to pre-establish the microstructure and reduce ReFe2 phase formation. This preliminary sintering step creates a favorable starting condition for the subsequent hot-deforming process, enabling better crystal grain orientation while minimizing harmful phase generation.
3Stability of the object's composition
If ReFe2 phase is present during hot-deforming, then material stability is maintained, but crystal grains cannot align with magnetization axis reducing remanent magnetization
Solution Approach 1:
The patent applies parameter changes by controlling the hot-deforming temperature (400-600°C) to be below the melting point of ReFe2 phase (1198K) while still sufficient for crystal grain alignment. This temperature parameter optimization allows the material to maintain stability during processing while enabling crystal grains to align with the magnetization axis, thereby achieving high remanent magnetization.
Solution Approach 2:
The patent applies partial action by allowing a small, controlled amount of ReFe2 phase to exist at the grain boundary (3-10 atomic percent Ce content) which provides material stability, while preventing excessive ReFe2 phase formation that would hinder crystal grain alignment. This balanced approach maintains both material stability and magnetic performance.
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 produces anisotropic rare-earth bulk magnets with excellent magnetic properties, including high remanent magnetization and maximum magnetic energy product, by minimizing ReFe2 phase and aligning crystal grains effectively.
Implementation Method 1
manufacturing an isotropic bulk magnet by press-sintering the amorphous magnetic powders
Implementation Method 2
manufacturing an anisotropic bulk magnet by hot-deforming the isotropic bulk magnet
Data Source
AI summary
Proposed are a method of manufacturing an anisotropic rare-earth bulk magnet, the method being capable of suppressing formation of ReFe2 phase, and an anisotropic rare-earth bulk magnet having excellent magnetic properties.