Sintered Re-Fe-B Magnet Grain-Boundary Rod Phases for Higher Coercivity
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Solution Overview
Problem
Existing methods for improving the coercivity of neodymium-iron-boron magnets face challenges due to the scarcity and high cost of heavy rare earth elements, and the formation of non-ferromagnetic boron-rich phases, which are detrimental to magnetic properties, and the control of cooling rates requires specialized equipment.
Innovation Solution
A sintered Re-Fe-B permanent magnet with a Ti-based precipitated phase in the form of Re-Fe-Ti-B rod-shaped objects, distributed in the grain boundary phase, controlled through a specific atomic percentage content and a preparation process involving grain boundary broadening and pulse aging heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements such as dysprosium and terbium are added to improve coercivity, then the coercivity of magnets is improved, but the scarcity and high cost of these elements limit their wide application
Solution Approach 1:
The patent changes the compositional parameters by using light rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd) instead of heavy rare earth elements (Dy, Tb). The specific atomic percentage ranges are optimized: Re 1-20 at%, Ti 40-90 at%, Fe 1-30 at%, B 10-20 at%, with Ti:B ratio of 4:1-9:1. This parameter change achieves comparable coercivity improvement without relying on scarce heavy rare earth elements.
Solution Approach 2:
The patent creates a composite structure with Re-Fe-Ti-B rod-shaped precipitated phases distributed in the grain boundary phase. This composite material approach combines light rare earth elements with Ti and B to form a new phase that provides coercivity enhancement, replacing the traditional heavy rare earth element addition strategy.
2Strength
If Ti and Zr elements are added to generate precipitated phases and reduce boron-rich phases, then the coercivity is improved, but the control of cooling rate requires specialized equipment and is difficult to implement
Solution Approach 1:
The patent changes the compositional parameters to achieve the desired phase structure without relying on controlled cooling rates. By optimizing the atomic percentages of Re (1-20 at%), Ti (40-90 at%), Fe (1-30 at%), and B (10-20 at%), with Ti:B ratio of 4:1-9:1, the Re-Fe-Ti-B rod-shaped precipitated phases form during conventional sintering processes, eliminating the need for specialized cooling rate control equipment.
3Strength
If the size of precipitated phase Ti-B rod-shaped objects is increased to improve coercivity, then the magnetic properties are improved, but the conventional production process cannot effectively control the precipitated phase morphology and distribution
Solution Approach 1:
The patent creates a composite structure with Re-Fe-Ti-B rod-shaped precipitated phases (length 100-300 nm) distributed in the grain boundary phase. This composite approach uses light rare earth elements combined with Ti and B to form a new phase that naturally develops the desired rod-shaped morphology and grain boundary distribution during conventional sintering, achieving both improved coercivity and manufacturing precision.
Solution Approach 2:
The patent optimizes compositional parameters (Re 1-20 at%, Ti 40-90 at%, Fe 1-30 at%, B 10-20 at%, Ti:B ratio 4:1-9:1) to control the formation of Re-Fe-Ti-B precipitated phases with specific morphology (rod-shaped, length 100-300 nm) and distribution (grain boundary phase). This compositional control enables the desired phase structure to form during conventional sintering without requiring specialized equipment for morphology control.
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 process enhances coercivity by preventing boron-rich phase formation and inhibiting grain growth, leading to improved magnetic properties and performance.
Implementation Method 1
the addition of some metal elements, such as Ti and Zr, which have very low solubility in the grain boundary phase, will generate additional precipitated phases with the B element
Implementation Method 2
grain boundary broadening and pulse aging heat treatment
Data Source
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AI summary
The invention provides a sintered Re-Fe-B permanent magnet, a preparation method thereof and application thereof. The sintered Re-Fe-B permanent magnet disclosed by the invention has a Ti system precipitated phase, and the Ti system precipitated phase comprises a Re-Fe-Ti-B rod-shaped object; the length of the Re-Fe-Ti-B rod-shaped object ranges from 100 nm to 300 nm; in the Ti-series precipitated phase, the atom percentage content of Re is 1-20 at%, the atom percentage content of Fe is 1-30 at%, the atom percentage content of Ti is 40-90 at%, and the atom percentage content of B is 10-20 at%; the atom percentage content ratio of Ti to B is 4: 1-9: 1. According to the sintered neodymium-iron-boron permanent magnet of the present disclosure, through combination of formula design and process optimization, a large-size Re-Fe-Ti-B rod-shaped object is formed, formation of a boron-rich phase is prevented, the Re-Fe-Ti-B rod-shaped object is only gathered in a grain boundary, grain size growth can be hindered, main phase grain growth can be inhibited, magnetic coupling response among main phase grains can be weakened, and the performance of the sintered Re-Fe-B permanent magnet is improved.