NdFeB Diffusion Source Composition for Low-Rare-Earth Coercivity Gain
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Solution Overview
Problem
The high cost and inefficiency of heavy rare earth element consumption in existing methods for improving the coercivity of NdFeB sintered permanent magnets, particularly due to the high demand and rising prices of Dy and Tb, necessitate a more effective and cost-efficient method for producing diffusion sources for grain boundary diffusion.
Innovation Solution
A novel method involving the preparation of a diffusion source material with a specific alloy composition (RαRHδMβBγFe100-α-β-γ-δ) and a coated alloy film, followed by heat treatment and crushing to produce a powdered diffusion source, which is applied to NdFeB magnets for thermal diffusion, reducing the proportion of Fe and increasing the proportion of M elements, thereby enhancing coercivity and diffusion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heavy rare earth elements Dy or Tb are added to the base alloy during production, then coercivity is improved, but heavy rare earth consumption increases and residual magnetism decreases
Solution Approach 1:
The invention divides the magnet structure into two distinct zones: the grain interior (without heavy rare earths) and the grain boundary region (with heavy rare earth enrichment). This segmentation allows heavy rare earth elements to be concentrated where they are most effective (at grain boundaries) rather than distributed throughout the entire alloy, thereby reducing overall consumption while maintaining coercivity enhancement.
Solution Approach 2:
The invention applies local quality by creating a non-uniform distribution of heavy rare earth elements specifically at the grain boundaries through diffusion. The grain boundary region receives enriched heavy rare earth content to improve coercivity, while the grain interior remains free of heavy rare earths to preserve residual magnetism, achieving optimal local properties in different regions.
2Strength
If pure Dy or Tb diffusion sources are used for grain boundary diffusion, then coercivity is improved, but production cost increases due to rising heavy rare earth prices
Solution Approach 1:
The invention changes the compositional parameters of the diffusion source material by incorporating Fe and B elements alongside heavy rare earths. This parameter modification creates a multi-component alloy system that reduces the heavy rare earth content requirement in the diffusion source while maintaining effective diffusion performance, thereby lowering production costs associated with pure heavy rare earth sources.
Solution Approach 2:
The invention develops composite diffusion source materials consisting of multiple elements (heavy rare earths, Fe, B, and other transition metals) rather than using pure heavy rare earths. This composite approach leverages synergistic effects among different elements to achieve effective coercivity enhancement at reduced heavy rare earth consumption, making the process more cost-effective.
3Ease of manufacture
If Fe proportion is increased in diffusion source material, then production cost decreases, but diffusion rate and utilization efficiency of heavy rare earths decrease
Solution Approach 1:
The invention optimizes the Fe content parameter within a specific range (5-20 wt%) rather than using high Fe concentrations. This controlled parameter adjustment allows sufficient cost reduction through Fe inclusion while preventing excessive Fe from inhibiting the diffusion rate of heavy rare earth elements, achieving a balanced optimization of both cost and diffusion performance.
Solution Approach 2:
The invention creates local quality differences by positioning Fe and B elements strategically in the diffusion source material composition to facilitate rather than hinder heavy rare earth diffusion. The specific compositional ratios and the presence of these elements create favorable local conditions for diffusion kinetics while maintaining cost efficiency.
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 method significantly reduces the residual magnetic loss, increases coercivity, and lowers production costs by improving the diffusion rate and utilization efficiency of heavy rare earths, with a typical increase in coercivity of ≥8kOe and minimal residual magnetic reduction.
Implementation Method 1
a thermally induced diffusion process has been developed which could significantly reduce the consumption of heavy rare earths
Implementation Method 2
c) performing a heat treatment of the coated alloy sheet
Data Source
AI summary
The invention relates to the technical field of NdFeB rare earth magnets, in particular to rare earth magnets with improved coercivity and its manufacturing method thereof. The invention further refers to a method of preparing a diffusion source material useful for preparing the NdFeB magnets.