Nd-Fe-B Magnet Grain Boundary Dysprosium Distribution
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Solution Overview
Problem
Current methods for producing sintered rare earth magnets, such as Nd—Fe—B, face limitations in achieving high temperature stability and magnetic properties due to the rapid degradation of magnetic remanence and coercivity, particularly with the limited availability and high cost of heavy rare earth elements like Dy and Tb.
Innovation Solution
A method involving hot isostatic pressing (HIP) is employed, where a core powder containing Nd, Fe, and B is combined with Dy or Tb, encapsulated, and subjected to a magnetic field and high pressure, allowing for increased Dy distribution along grain boundaries, thereby enhancing coercivity and thermal stability without the need for high temperatures or extensive processing times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heavy rare earth elements (Dy, Tb) are added to improve high temperature magnetic properties, then coercivity and thermal stability are improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies local quality by concentrating heavy rare earth elements specifically at the grain boundaries rather than uniformly distributing them throughout the magnet. This localized approach ensures that the expensive Dy or Tb elements are placed only where they are most effective for maintaining coercivity at high temperatures, while minimizing overall material cost.
Solution Approach 2:
The patent changes the distribution parameter of heavy rare earth elements from uniform to non-uniform, creating a gradient concentration where the highest concentration is at the grain boundaries. This parameter change allows achieving the same magnetic performance with less total heavy rare earth material, reducing cost.
2Reliability
If heavy rare earth elements are added to increase coercivity, then magnetic remanence decreases
Solution Approach 1:
By localizing heavy rare earth elements at grain boundaries, the patent achieves coercivity enhancement without the bulk material substitution that would reduce magnetic remanence. The grain boundary localization ensures that the interior of the grains, which contributes to remanence, remains rich in magnetically active Nd-Fe-B phase.
Solution Approach 2:
The patent segments the function of heavy rare earth elements from bulk material substitution to boundary-specific reinforcement. This segmentation allows coercivity improvement at grain boundaries while preserving the magnetic remanence properties of the bulk Nd-Fe-B grains.
3Manufacturing precision
If traditional sintering methods are used to achieve fine microstructure, then processing time and temperature are high, but manufacturing efficiency is reduced
Solution Approach 1:
The patent applies preliminary action by pre-forming the magnet components using additive manufacturing or other near-net-shape processes before final sintering. This preliminary shaping reduces the extent of subsequent processing needed and allows for optimized sintering parameters that achieve fine microstructure more quickly.
Solution Approach 2:
The patent changes the sintering parameters (temperature, time, atmosphere) to optimize for both fine microstructure and reduced processing time. By carefully controlling these parameters, the patent achieves the desired microstructural fineness with shorter holding times and potentially lower peak temperatures.
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
This approach results in improved high-temperature magnetic properties and reduced processing costs by allowing for a lower temperature and shorter processing time, effectively increasing coercivity and maintaining magnetic remanence, which is crucial for traction motor applications in hybrid electric vehicles.
Implementation Method 1
A magnetic field is applied during encapsulating and thereafter to the powder combination to align the magnetic dipoles therein
Implementation Method 2
The encapsulated powder combination is isostatically pressed while heating such that the temperature of the powder combination increases from a first temperature to a second temperature
Implementation Method 3
The encapsulated powder combination is isostatically pressed while heating
Data Source
AI summary
A method of making a magnetic material includes a step of providing a first material in the form of a core powder containing Nd, Fe and B. The first material is combined with the second material to form a powder combination. The second material includes a component selected from the group consisting of Dy, Tb, and combinations thereof. The powder combination is encapsulated to form an encapsulated powder combination. A magnetic field is applied to the powder combination during encapsulation and thereafter to align the magnetic dipoles therein. The encapsulated powder combination is isostatically pressed with heat to form the magnetic material.