NdFeB Magnet Corrosion Resistance via Grain Boundary Refractory Metals
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Solution Overview
Problem
Existing NdFeB magnets exhibit low corrosion resistance against air, moisture, and salt, particularly at high temperatures, limiting their application in generators and electric motors.
Innovation Solution
A bi-phase alloy sintering method is employed to distribute refractory metals like Nb, Zr, Ti, or Mo primarily in the grain boundary phase of NdFeB magnets, enhancing high-temperature corrosion resistance without compromising magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refractory metals are added to improve corrosion resistance, then corrosion resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific refractory metals (Nb, Zr, Ti, Cr, or Mo) at controlled concentrations (0.1-5.0 at%) to the NdFeB alloy system. This parameter modification enhances corrosion resistance by forming protective oxide layers on the grain boundaries while maintaining the sintering process framework, thus improving reliability without excessive manufacturing complexity
Solution Approach 2:
The invention creates a composite microstructure where refractory metal-containing phases are distributed along the grain boundaries of the NdFeB main phase. This composite structure combines the high magnetic performance of NdFeB with the corrosion resistance of refractory metal oxides, achieving both improved reliability and controlled manufacturing complexity through a targeted composite material design
2Reliability
If refractory metals are added to enhance corrosion resistance, then corrosion resistance is improved, but production cost increases
Solution Approach 1:
The invention optimizes the concentration parameters of refractory metals to a narrow range (0.1-5.0 at%), which is sufficient to form effective protective oxide layers on grain boundaries. This parameter optimization achieves the desired corrosion resistance improvement while minimizing the addition of expensive refractory metals, thus balancing reliability enhancement with production cost control
Solution Approach 2:
The invention applies refractory metals locally at the grain boundaries rather than uniformly throughout the bulk material. This local quality approach concentrates the corrosion protection function where it is most needed (at grain boundaries which are susceptible to intergranular corrosion) while minimizing the overall amount of expensive refractory metals required, thereby improving reliability without excessive production cost increase
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 improves high-temperature corrosion resistance and maintains magnetic properties, outperforming prior art by reducing surface corrosion and magnetic flux loss, while keeping production costs manageable.
Implementation Method 1
Common NdFeB magnets have a low corrosion resistance against air (mainly O2), moisture and salt
Implementation Method 2
a bi-phase alloy sintering method is employed to distribute refractory metals like Nb, Zr, Ti, or Mo primarily in the grain boundary phase
Data Source
AI summary
The present invention provides high corrosion resistant sintered NdFeB magnets and preparation process thereof. The composition of said magnets by mass% is NdxRxlFe100-(x + xl + y + yl + z)TyMylBz, wherein 24 ≤ x ≤ 33, 0 ≤ x1 ≤ 15, 1.43 ≤ y ≤ 16.43, 0.1 ≤ yl ≤ 0.6, 0.91 ≤ z ≤ 1.07, R is one or more selected from the group consisting of Dy, Tb, Pr, Ce and Gd, T is one or more selected from the group consisting of Co, Cu and Al, M is one or more selected from the group consisting of Nb, Zr, Ti, Cr and Mo, and M is distributed within the grain boundary phase of the NdFeB magnets.