Sm-Co Magnet Composition and Sintering for High Coercivity
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Solution Overview
Problem
Conventional methods for manufacturing Sm-Co-based magnets face challenges in achieving high coercive force, magnetization, and squareness ratio while maintaining a high Fe concentration, often resulting in deteriorated magnetic properties due to phase separation and precipitation of α-Fe.
Innovation Solution
A method involving a composition formula R p Fe q M r Cu t Co 100-p-q-r-t, where R represents rare earth elements, M is Zr, Ti, or Hf, and specific atomic ratios, with a sintering process under controlled temperature and pressure conditions to form a metallic structure with a Th2Zn17 crystal phase and Cu-rich phases, enhancing coercive force and squareness ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the concentration of Fe is increased to achieve higher magnetization, then magnetization is improved, but the squareness ratio deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the Fe concentration within 22-35 atomic percent and applying a specific heat treatment process (holding at 1123-1273 K for 0.5-24 hours) to transform the metallic structure. This resolves the contradiction by finding the optimal parameter range where high magnetization is achieved while maintaining good squareness ratio through the formation of a specific cellular structure with Cu-rich phases at grain boundaries
Solution Approach 2:
The patent creates a composite metallic structure consisting of Th2Zn17-type main phase with Cu-rich phases distributed at grain boundaries and cellular structures. This composite structure allows the Fe-rich main phase to provide high magnetization while the Cu-rich boundary phases maintain structural integrity and magnetic domain wall pinning, thus achieving both high magnetization and good squareness ratio
2Strength
If the concentration of Fe is increased to achieve higher magnetization, then magnetization is improved, but phase separation and precipitation of α-Fe occur
Solution Approach 1:
The patent controls the Fe concentration within 22-35 atomic percent and applies specific heat treatment parameters (temperature 1123-1273 K, time 0.5-24 hours) to prevent α-Fe precipitation. By optimizing these parameters, the patent achieves high magnetization through increased Fe content while maintaining phase stability and preventing harmful phase separation
Solution Approach 2:
The patent creates local quality differences by forming Cu-rich phases specifically at grain boundaries and cellular structures, while maintaining a homogeneous Th2Zn17-type main phase in the interior. This local distribution of Cu-rich phases at boundaries prevents α-Fe precipitation in the main phase while allowing high Fe content for high magnetization
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 effectively suppresses magnetization deterioration, achieving high coercive force and squareness ratio even at high Fe concentrations, with improved magnetic domain wall pinning and thermal stability, leading to enhanced performance in Sm-Co-based magnets.
Implementation Method 1
sintering a green compact corresponding in composition to the composition formula defined above by performing a heat treatment by holding the green compact at a temperature of not lower than 1180°C nor higher than 1220°C under an inert gas atmosphere for not less than 3 hours nor more than 15 hours
Implementation Method 2
performing a heat treatment by holding the green compact at a temperature of not lower than 1180°C nor higher than 1220°C
Data Source
Figure 1~2
Figure 3~4
AI summary
There is provided a high-performance permanent magnet. The permanent magnet expressed by a composition formula: RpFeqMrCutCo100-p-q-r-t. The magnet comprises a metallic structure including crystal grains which constitutes a main phase having a Th2Zn17 crystal phase. An average value of Fe concentrations in the crystal grains of 20 or more is 28 atomic percent or more and an average value of R element concentrations in the crystal grains of 20 or more is 10 atomic percent or more.