Low-B R-Fe-B Sintered Magnet Grain Boundary Phase for Higher Hcj
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Solution Overview
Problem
R-T-B-based sintered magnets face challenges in increasing Hcj and Br while reducing the usage of heavy rare earth elements like Dy and Tb, which are limited and expensive, and existing research on R-T-Ga phases has inconsistent results due to varying compositions and performance.
Innovation Solution
An R—Fe—B-based sintered magnet with optimized content ranges of R, B, Co, Cu, Ga, and Ti is developed, forming an R6-T13−δM1+δ series phase with a high volume fraction in grain boundaries, enhancing Hcj and Br by suppressing impurity phases and optimizing grain boundary distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth elements such as Dy and Tb are added to improve Hcj, then Hcj increases, but residual magnetic flux density Br decreases and cost increases
Solution Approach 1:
The patent changes the chemical composition parameters by limiting B content to 0.86-0.94 wt% and optimizing heavy rare earth content to 0.1-0.5 wt%, while introducing Ga (0.3-0.5 wt%) and Cu (0.2-0.45 wt%) to form a specific R6-T13-δM1+δ phase structure that achieves high Hcj without sacrificing Br
Solution Approach 2:
The patent creates a composite microstructure consisting of R2Fe14B main phase grains surrounded by an R6-T13-δM1+δ grain boundary phase (where M is primarily Ga with some Cu), which combines the high coercivity contribution from the grain boundary phase with the high flux density contribution from the main phase, resolving the contradiction between Hcj and Br
2Force
If B content is reduced to form R-T-Ga phase, then Hcj increases, but excessive R-T-Ga phase formation hinders further Hcj improvement and requires precise composition control
Solution Approach 1:
The patent precisely controls the B content parameter within 0.86-0.94 wt% to prevent excessive formation of R-T-Ga phase, and optimizes Ga content to 0.3-0.5 wt% to ensure sufficient R6-T13-δM1+δ phase formation at grain boundaries, achieving high Hcj with manageable composition complexity
Solution Approach 2:
The patent introduces Cu as an intermediary element (0.2-0.45 wt%) that works synergistically with Ga to form the R6-T13-δM1+δ phase, where Cu helps stabilize the phase structure and facilitates the formation process, making the composition control more robust
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 solution significantly improves the magnetic properties of R—Fe—B-based sintered magnets by increasing Br and Hcj while reducing the content of heavy rare earth elements, achieving a more uniform and continuous grain boundary distribution and de-magnetic-coupling effect.
Implementation Method 1
forming an R6-T13−δM1+δ series phase of a special composition and increasing its volume fraction in grain boundary phases... achieving a more uniform and continuous grain boundary distribution and de-magnetic-coupling effect
Implementation Method 2
a method for preparing an R—Fe—B-based sintered magnet with a low B content... sintering the formed body in a vacuum or inert gas at a temperature of 900° C.-1100° C. followed by heat treatment
Data Source
AI summary
Disclosed are an R—Fe—B-based sintered magnet with a low B content and a preparation method therefor. The sintered magnet comprises the following components: 28.5 wt %-31.5 wt % of R, 0.86 wt %-0.94 wt % of B, 0.2 wt %-1 wt % of Co, 0.2 wt %-0.45 wt % of Cu, 0.3 wt %-0.5 wt % of Ga, 0.02 wt %-0.2 wt % of Ti, and 61 wt %-69.5 wt % of Fe. The sintered magnet has an R6-T13−δM1+δ series phase accounting for 75% or more of the total volume of grain boundaries. The present invention selects optimal content ranges of R, B, Co, Cu, Ga, and Ti, and forms an R6-T13−δM1+δ series phase of a special composition and increases its volume fraction in grain boundary phases, so as to acquire higher Hcj and SQ values.