Neodymium Iron Boron Magnet Coercive Force via Surface RTMH Alloy Diffusion
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Solution Overview
Problem
Current methods for enhancing the coercive force of neodymium iron boron magnets often reduce magnetic remanence and maximum magnetic energy product, and involve wasteful use of heavy rare earth resources.
Innovation Solution
A method involving the application of an RTMH alloy layer or a mixture of light and heavy rare earths onto the surface of neodymium iron boron magnets, followed by heat treatment, to enhance coercive force while maintaining magnetic remanence and energy product, using a specific formulation and process that includes mixing alloy powders with organic solvents and coating onto the magnet blanks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If heavy rare earth is added during smelting to enhance coercive force, then coercive force is improved, but magnetic remanence and magnetic energy product are reduced
Solution Approach 1:
The patent applies preliminary action by coating the magnet surface with rare earth alloy powder before final sintering. The coating layer is prepared in advance and then diffused into the magnet during a controlled heat treatment process (800-950°C for 5-15 minutes), allowing the rare earth elements to penetrate and strengthen the magnet structure without requiring heavy rare earth addition during initial smelting.
Solution Approach 2:
The patent implements local quality by concentrating the rare earth alloy treatment specifically at the magnet surface through coating. This creates a localized high-concentration rare earth layer at the surface that diffuses inward, providing enhanced coercive force where it is most needed while keeping the bulk composition optimized for magnetic remanence and energy product.
2Force
If heavy rare earth is added during smelting to enhance coercive force, then coercive force is improved, but heavy rare earth resources are wasted
Solution Approach 1:
The patent extracts the rare earth enhancement function from the bulk smelting process and relocates it to a surface coating process. Instead of mixing heavy rare earth throughout the entire magnet during smelting (which is wasteful), the method extracts and applies rare earth alloy powder specifically to the surface, then diffuses it only where needed during a brief heat treatment.
Solution Approach 2:
The patent changes the processing parameters from high-temperature smelting (where heavy rare earth would be dispersed throughout the bulk) to a controlled low-temperature diffusion process (800-950°C for 5-15 minutes). This parameter change allows rare earth elements to be efficiently utilized at the surface without requiring excessive amounts or heavy rare earth substitution.
3Quantity of substance
If sintering temperature is increased to improve magnet properties, then magnetic properties are enhanced, but grain boundary structure deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-coating the magnet surface with rare earth alloy powder before the brief diffusion heat treatment. This ensures that the rare earth elements are already positioned at the surface and ready to diffuse inward during the short high-temperature exposure, maximizing their beneficial effect without requiring prolonged high-temperature sintering that would damage grain boundaries.
Solution Approach 2:
The patent changes the sintering parameters from traditional high-temperature long-duration processing to a controlled lower-temperature (800-950°C) short-duration (5-15 minutes) diffusion treatment. This parameter optimization allows sufficient rare earth diffusion into the grain boundaries to enhance coercive force while avoiding excessive grain growth and structural deterioration.
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 significantly enhances coercive force by up to 51% while keeping magnetic remanence and maximum magnetic energy product essentially constant, and reduces the cost by conserving heavy rare earth resources.
Implementation Method 1
a neodymium iron boron magnet comprising a neodymium iron boron magnet blank and an RTMH alloy layer compounded on the surface of the blank
Implementation Method 2
followed by heat treatment, to enhance coercive force while maintaining magnetic remanence and energy product
Data Source
Figure 1
Figure 2
AI summary
The present invention, on the one hand, provides a neodymium iron boron magnet, comprising neodymium iron boron magnet blank and the RTMH alloy layer compounded on the surface; the R is one or more selected from rare earth elements; the T is Fe and/or Co; the M is one or more selected from the group consisting of Al, Si, Ti, V, Cr, Mn, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pt, Au, Pb and Bi; the H is hydrogen element. By the present invention, the coercive force of magnets is significantly enhanced, and at the same time, the original magnetic remanence and maximum magnetic energy product of the magnets are not significantly reduced.