Nd-Fe-B Magnet Grain Structure for Higher Coercivity
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Solution Overview
Problem
R-T-B based permanent magnets, particularly hot deformed magnets, do not achieve the anticipated high coercivity due to the distribution of R-rich phases parallel to the easy magnetization axis, which affects the coercivity.
Innovation Solution
The R-T-B based permanent magnet is designed with R-rich phases located between main phase grains, where the average interval of R-rich phases is between 30 μm to 1,000 μm perpendicular to the easy magnetization axis, and the main phase grains have short axes ranging from 20 nm to 200 nm, with controlled concentrations and compositions to enhance coercivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the super-rapid cooling and solidification method is used to produce alloy ribbons with fine crystals, then the crystal grain size is reduced, but the coercivity does not increase as expected
Solution Approach 1:
The invention applies local quality by creating a specific distribution pattern of R-rich phases at grain boundaries. Instead of uniform distribution, the R-rich phases are strategically positioned between main phase grains with controlled intervals (30-1000 μm), creating localized magnetic isolation zones that prevent magnetization reversal propagation while maintaining fine grain structure
Solution Approach 2:
The invention changes the parameter of R-rich phase distribution by controlling the interval between phases to be within 30-1000 μm perpendicular to the easy magnetization axis. This parameter optimization ensures that the R-rich phases are spaced sufficiently to isolate main phase grains magnetically, thereby achieving the expected coercivity enhancement from fine grain structures
2Manufacturing precision
If R-rich phases are present in the magnet structure, then grain boundary control is improved, but coercivity is reduced due to improper distribution
Solution Approach 1:
The invention applies preliminary action by establishing the R-rich phase distribution pattern before final magnetization. The R-rich phases are positioned between main phase grains during manufacturing with predetermined intervals, creating a pre-configured magnetic isolation structure that prevents magnetization reversal propagation
Solution Approach 2:
The invention optimizes the parameter of R-rich phase interval to 30-1000 μm perpendicular to the easy magnetization axis. This specific parameter range ensures that R-rich phases provide sufficient magnetic isolation between grains while maintaining proper grain boundary control, thereby resolving the contradiction between grain boundary control and coercivity
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
This configuration results in a significant increase in coercivity and residual magnetic flux density, while maintaining a high squareness ratio and temperature stability, outperforming magnets with similar compositions in the related art.
Implementation Method 1
Each of the plurality of R-rich phases is located between the plurality of main phase grains... An average value of intervals between the plurality of R-rich phases in a direction substantially perpendicular to the easy magnetization axis direction is from 30 μm to 1,000 μm
Implementation Method 2
In the super-rapid cooling and solidification method, a molten metal of an R-T-B based alloy is rapidly cooled on a surface of a cooled roll. As a result, the molten metal is solidified to form alloy ribbons
Implementation Method 3
a molten metal of an R-T-B based alloy is rapidly cooled on a surface of a cooled roll
Data Source
AI summary
A permanent magnet includes a rare earth element R; a transition metal element T; and B. The permanent magnet includes Nd as R. The permanent magnet includes Fe as T. The permanent magnet contains main phase grains and R-rich phases. The main phase grains include R, T, and B. The R-rich phases include R. The main phase grains observed in a cross section of the permanent magnet are flat. The cross section is parallel to an easy magnetization axis direction of the permanent magnet. Each of the R-rich phases is located between the main phase grains. An average value of intervals between the R-rich phases in a direction substantially perpendicular to the easy magnetization axis direction is from 30 μm to 1,000 μm. An average value of lengths of short axes of the main phase grains observed in the cross section is from 20 nm to 200 nm.