ThMn12 Permanent Magnet Composition for High Coercivity
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Solution Overview
Problem
Existing permanent magnets with a ThMn12-type tetragonal structure face challenges in achieving high coercivity and heat resistance, despite advancements in saturation magnetization and temperature characteristics.
Innovation Solution
A permanent magnet with a composition represented by Formula (R1-xZrx)a(T1-yMy)bBc, where R is a rare earth element, T includes Fe and Co, M stabilizes the ThMn12-type crystal structure, and B is concentrated in the grain boundaries to form amorphous phases, enhancing coercivity and heat resistance, manufactured through quenching, pulverization, molding, sintering, and heat-treating processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a ThMn12-type tetragonal structure is used to achieve high saturation magnetization, then saturation magnetization is improved, but coercivity is insufficient
Solution Approach 1:
The patent applies local quality by creating an amorphous phase specifically at the grain boundaries while maintaining the crystalline ThMn12-type structure in the grain interiors. This localized structural difference allows the grain boundaries to provide enhanced coercivity through pinning effects, while the crystalline grains maintain high saturation magnetization. The amorphous phase is formed by concentrating specific elements (B, Si, Al, Ti, V, Cr, Mn, Cu, Hf, Nb, Mo, Ta, or W) at the grain boundaries through controlled composition design.
Solution Approach 2:
The patent employs composite materials by combining the crystalline ThMn12-type phase with an amorphous phase at the grain boundaries. This composite structure leverages the advantages of both phases: the crystalline phase provides high saturation magnetization and magnetic anisotropy, while the amorphous phase enhances coercivity through domain wall pinning. The composite nature is achieved by carefully selecting the composition parameters (a, b, c, x, y) to ensure phase separation and amorphous phase formation at grain boundaries.
2Stability of the object's composition
If conventional compositions are used to maintain structural stability, then structural stability is preserved, but coercivity and heat resistance are insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the compositional parameters within specific ranges to achieve the desired microstructure and properties. The composition is defined by Formula (1) with constrained parameters: 5≤a≤12, b=100-(a+c), 0.1≤c≤20, 0.01≤x≤0.5, and 0.01≤y≤0.5. These parameter ranges ensure structural stability while enabling the formation of amorphous grain boundaries that enhance coercivity and heat resistance. The parameter optimization balances phase stability with performance enhancement.
3Reliability
If grain boundaries are refined to improve magnetic properties, then coercivity may improve, but manufacturing complexity increases
Solution Approach 1:
The patent simplifies the manufacturing process by using parameter changes in the composition rather than complex processing steps to achieve amorphous grain boundaries. By adjusting the chemical composition parameters (adding specific elements and controlling their concentrations), the amorphous phase forms naturally during conventional solidification and heat treatment processes. This approach avoids the need for specialized grain boundary engineering techniques while still achieving the desired microstructure and magnetic properties.
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 results in a permanent magnet with significantly improved coercivity and Curie temperature, exceeding 400°C, while maintaining high saturation magnetization and stability of the ThMn12-type crystal structure, effectively addressing the limitations of existing magnets.
Implementation Method 1
the grain boundary contains an amorphous phase
Implementation Method 2
a step (II) of quenching the molten metal at a rate of 102 to 107 K/sec and thereby forming an alloy thereof
Implementation Method 3
a step (VI) of heat-treating the sintered body and then quenching the sintered body
Data Source
AI summary
A permanent magnet having a high coercivity, a method for manufacturing such a permanent magnet, and a device using such a permanent magnet are provided. The permanent magnet has a composition represented by a below-shown Formula (1). Formula (1): (R1-xZrx)a(T1-yMy)bBc. In Formula (1); R is at least one element selected from rare earth elements; T is at least one element selected from a group consisting of Fe, Co and Ni; M is at least one element selected from a group consisting of Al, Si, Ti, V, Cr, Mn, Cu, Hf, Nb, Mo, Ta and W; and each of a, b and c indicates atomic %, and x and y indicate ratios of Zr and M, respectively; and they are numbers that satisfy below-shown Expressions, 5≤a≤12, b=100−(a+c), 0.1≤c≤20, 0.01≤x≤0.5, and 0.01≤y≤0.5.