R-T-B Rare Earth Sintered Magnet Grain Boundary Diffusion
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Solution Overview
Problem
Conventional R-T-B rare earth sintered magnets experience a decrease in coercivity at temperatures above room temperature, and the use of heavy rare earth elements to improve coercivity disrupts the balance between demand and supply, leading to increased prices and instability in securing sufficient amounts.
Innovation Solution
A method of manufacturing R-T-B rare earth sintered magnets by sintering a compact of alloy powder with a grain boundary phase component in a sintering furnace, where the grain boundary phase component with a higher R content is diffused to surround the main phase grains, enhancing coercivity without relying heavily on heavy rare earth elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements (Dy, Tb) are added to improve coercivity, then coercivity is improved, but the balance between demand and supply is disrupted, leading to sharp price rises and instability in securing sufficient amounts
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at the grain boundaries through diffusion treatment, rather than uniformly distributing them throughout the magnet. This localized approach achieves the necessary coercivity improvement at the critical grain boundary regions while using minimal amounts of heavy rare earth elements, thus maintaining supply stability.
Solution Approach 2:
The patent changes the distribution parameter of heavy rare earth elements from uniform distribution to concentrated distribution at grain boundaries. By controlling the diffusion process and heat treatment parameters, the invention achieves optimal coercivity with reduced overall heavy rare earth content, resolving the contradiction between performance and supply stability.
2Strength
If heavy rare earth elements are added to improve coercivity, then coercivity is improved, but the amount of heavy rare earth elements used increases, disrupting supply balance
Solution Approach 1:
The invention concentrates heavy rare earth elements specifically at grain boundaries where they are most effective for improving coercivity. This localized enrichment achieves the desired magnetic performance with significantly reduced overall quantities of heavy rare earth elements compared to uniform distribution approaches.
Solution Approach 2:
The patent creates a composite structure with two distinct phases: a main phase matrix and a grain boundary phase enriched with heavy rare earth elements. This composite approach allows the heavy rare earth elements to be strategically positioned where they provide maximum coercivity enhancement while minimizing the total amount required.
3Strength
If grain boundary phase component is diffused to surround main phase grains, then coercivity is improved and magnetic property variation is reduced, but the sintering process complexity increases
Solution Approach 1:
The patent incorporates the grain boundary phase component into the initial alloy composition before sintering. This preliminary incorporation eliminates the need for separate post-sintering diffusion treatments, achieving the desired grain boundary enrichment through the sintering process itself and thereby reducing overall process complexity.
Solution Approach 2:
The invention merges the sintering process with the grain boundary phase formation process. By combining these operations into a single integrated process, the patent achieves coercivity improvement without adding separate diffusion treatment steps, thus avoiding increased process complexity.
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 R-T-B magnets with improved coercivity and reduced variation in magnetic properties, allowing for stable and efficient use in applications like motors and generators without excessive reliance on costly heavy rare earth elements.
Implementation Method 1
The grain boundary phase component supplied to the compact is diffused to peripheries of main phase grains having a composition of R 2 Fe 14 B
Implementation Method 2
a sintering step of disposing and sintering the compact and an alloy material of a second alloy in a chamber of a sintering furnace to turn the compact into a sintered body
Data Source
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AI summary
A method of manufacturing an R-T-B rare earth sintered magnet includes a process of disposing and sintering a compact of a first alloy powder and an alloy material of a second alloy in a chamber of a sintering furnace. The first alloy consists of R which represents a rare earth element, T which represents a transition metal essentially containing Fe, a metal element M which represents Al and/or Ga, B, Cu, and inevitable impurities. The first alloy contains 11 at% to 17 at% of R, 4.5 at% to 6 at% of B, 0 at% to 1.6 at% of M, and T as the balance, and Dy content in all of the rare earth elements is 0 at% to 29 at%. The second alloy consists of R which represents a rare earth element, T which represents a transition metal essentially containing Fe, a metal element M which represents Al and/or Ga, B, Cu, and inevitable impurities. The second alloy contains 11 at% to 20 at% of R, 4.5 at% to 6 at% of B, and 0 at% to 1.6 at% of M, and T as the balance, and Dy content in all of the rare earth elements is 0 at% to 29 at%.