NdFeB Magnet Alloy Microstructure for Coercive Force and Rectangularity
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Solution Overview
Problem
Nd—Fe—B sintered magnets exhibit room for improvement in rectangularity and magnetic properties, particularly in high-performance applications like motors.
Innovation Solution
An R-T-B based alloy with specific compositions and microstructural features, including regions with high Cu and Co concentrations in the R-rich phase and grain boundary phases, and controlled distribution of heavy rare earth elements like Tb or Dy, is used to enhance coercive force and residual magnetic flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the amount of rare earth element in metal state is increased to improve coercive force, then coercive force is improved, but rectangularity in magnetization curve deteriorates
Solution Approach 1:
The patent applies local quality by creating specific regional distributions of elements within the magnet structure. Region A with high Cu concentration (0.5 at% or more) occupies 80% or more of the R-rich phase area, and region B with high Co concentration (2.5 at% or more) occupies 60% or more of region A. This localized element distribution optimizes both coercive force and rectangularity simultaneously, resolving the contradiction between improving coercive force and maintaining rectangularity.
2Reliability
If conventional production methods are used to achieve basic magnetic properties, then basic magnetic properties are obtained, but rectangularity and overall magnetic performance remain insufficient for high-performance applications
Solution Approach 1:
The patent employs parameter changes by precisely controlling the concentrations and distributions of multiple elements (Cu, Co, heavy rare earth elements like Tb or Dy) within specific regions. The maximum element concentration of Cu in grain boundary phase is controlled at 1 to 5 at%, and the concentration distribution curves of Cu and heavy rare earth elements are optimized with a specific half-value width difference. These parameter optimizations enable the magnet to achieve both basic magnetic properties and superior rectangularity for high-performance applications.
Data Source
AI summary
Provided is a sintered magnet that is an R-T-B based sintered magnet having a region having a concentration of at least one heavy rare earth element decreasing from the surface toward the inside, in which the at least one heavy rare earth element includes at least either of Tb or Dy, R includes Nd, T includes Fe, Co, and Cu, there is a grain boundary phase containing at least either of Tb or Dy and Nd between two main phase particles, and a value obtained by subtracting a half value width of a concentration distribution curve of Cu from a half value width of a concentration distribution curve of Tb or Dy in a part including the grain boundary phase is from 10 to 20 nm.