Sm2Co17 Magnet Copper-Rich Phase Control
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Solution Overview
Problem
Sm2Co17 type permanent magnets with high iron concentration exhibit a steep rising initial magnetization curve, which is undesirable for variable magnetic flux motors and generators, and are costly due to high cobalt content, necessitating a composition that balances coercive force, magnetic flux density, and cost while controlling the copper-rich phase precipitation intervals.
Innovation Solution
A permanent magnet composition with a Th2Zn17 crystal phase and copper-rich CaCu5 phase, where the average distance between copper-rich phases is less than 120 nm, and specific elemental ratios are used to control coercive force and magnetic flux density, incorporating elements like samarium, titanium, and zirconium to optimize magnetic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If iron concentration is increased to improve magnetic flux density and reduce cost, then magnetic flux density is improved and cost is reduced, but the initial magnetization curve rises steeply which is undesirable for variable magnets
Solution Approach 1:
The patent applies parameter changes by precisely controlling the composition ratios of elements (Fe: 25-40 atomic%, Cu: 5-15 atomic%, Co: 30-50 atomic%, R: 5-15 atomic%, M: 0.1-5 atomic%) and heat treatment parameters (solution treatment at 1100-1300°C, aging at 600-900°C) to achieve the desired balance between magnetic flux density and initial magnetization curve gradient. By adjusting these parameters, the patent optimizes the two-phase structure to suppress the steep rising of the initial magnetization curve while maintaining high magnetic flux density.
Solution Approach 2:
The patent uses composite materials by creating a two-phase structure consisting of a Th2Zn17-type crystal phase and a copper-rich CaCu5-type crystal phase. This composite structure combines the high magnetic flux density characteristics of iron-rich phases with the coercive force enhancement from copper-rich phases, while the specific phase distribution and morphology control the initial magnetization curve gradient to be suitable for variable magnet applications.
2Force
If cobalt content is increased to improve coercive force, then coercive force is improved, but cost increases significantly
Solution Approach 1:
The patent applies parameter changes by optimizing the cobalt content to a specific range (30-50 atomic%) and introducing alternative elements M (Ti, Zr, Hf) at controlled amounts (0.1-5 atomic%) that can partially substitute for cobalt. The heat treatment parameters are also optimized to maximize the coercive force contribution from the copper-rich phases, thereby reducing the amount of expensive cobalt needed while maintaining high coercive force.
Solution Approach 2:
The patent employs cheaper elements (Fe, Cu, and alternative M elements like Ti, Zr, Hf) to replace expensive cobalt while achieving the desired magnetic properties. The composition is designed to use abundant elements in optimized ratios that provide comparable or superior performance to high-cobalt formulations, thereby reducing material cost.
3Ease of manufacture
If copper-rich phase precipitation intervals are controlled to suppress initial magnetization curve rising, then the initial magnetization curve gradient is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by performing solution treatment before aging treatment. The solution treatment at 1100-1300°C for 0.5-10 hours pre-dissolves the alloying elements and creates a homogeneous solid solution, which prepares the material for controlled precipitation during the subsequent aging treatment. This preliminary step ensures uniform distribution of copper-rich phases during aging, making it easier to control the phase distribution and initial magnetization curve gradient.
Solution Approach 2:
The patent utilizes phase transitions by controlling the aging treatment to precipitate copper-rich CaCu5-type crystal phases from the solid solution. The aging temperature (600-900°C) and time (0.5-10 hours) are optimized to control the nucleation and growth of these phases, achieving the desired precipitation intervals and distribution that suppress the initial magnetization curve gradient while maintaining manufacturability.
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 suppresses the steep rising of the initial magnetization curve, achieving a moderate coercive force range of 200 kA/m to 500 kA/m and a pinning rate of 50% or more, suitable for variable magnets, while reducing costs by increasing iron concentration and maintaining high coercive force.
Implementation Method 1
an Sm2Co17 type magnet has a two-phase separation structure of a 2-17 crystal phase and a 1-5 type crystal phase, and obtains magnetic characteristics by a coercive force exhibition mechanism of magnetic domain wall pinning type
Implementation Method 2
a structure including a Th2Zn17 crystal phase (2-17 type crystal phase) and a copper-rich phase (CaCu5 crystal phase (1-5 type crystal phase) and the like) having a copper concentration in a range from 1.2 times to 5 times a copper concentration in the Th2Zn17 crystal phase
Data Source
AI summary
In an embodiment, a permanent magnet includes a composition represented by a composition formula: R(FepMqCur(Co1-sAs)1-p-q-r)z, where, R is at least one element selected from rare earth elements, M is at least one element selected from Ti, Zr, and Hf, A is at least one element selected from Ni, V, Cr, Mn, Al, Si, Ga, Nb, Ta, and W, 0.05≦p≦0.6, 0.005≦q≦0.1, 0.01≦r≦0.15, 0≦s≦0.2, and 4≦z≦9, and a two-phase structure of a Th2Zn17 crystal phase and a copper-rich phase. In a cross-section of the permanent magnet containing a crystal c axis of the Th2Zn17 crystal phase, an average distance between the copper-rich phases is 120 nm or less.