R-Fe-B Sintered Magnet Composition for High Br and Stable Coercivity
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Solution Overview
Problem
Existing R-Fe-B-type sintered magnets face challenges in achieving high residual flux density (Br) while maintaining coercivity (HcJ), as reducing the amount of rare-earth elements like Dy and Tb leads to decreased sinterability and abnormal grain growth, and existing methods to enhance HcJ often compromise Br or are resource-intensive.
Innovation Solution
Optimizing the structural morphology of R-Fe-B-type sintered magnets by adjusting the ratios of constituent elements, including R2Fe14B intermetallic compound and grain boundary phases, to achieve both high Br and stable HcJ, with specific compositions and production processes to control phase formation and grain growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of heavy rare-earth elements (Dy, Tb) is reduced to increase Br, then the residual flux density increases, but the coercivity decreases and sinterability deteriorates
Solution Approach 1:
The invention changes the chemical composition parameters by adding specific elements (Co, Ni, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb, or Bi) at controlled concentrations (0.01-5.0 wt%) to the R-Fe-B magnet system. This parameter modification enables achieving high Br (≥1.45 T) while maintaining adequate HcJ (≥900 kA/m) without relying on heavy rare-earth elements, thus resolving the contradiction between increasing Br and maintaining HcJ
Solution Approach 2:
The invention creates a composite material system by combining rare-earth elements (R: Nd, Pr, La, Ce, Gd, Dy, Tb, Ho, Er, Tm, Y, or mixtures) with transition metals (Co, Ni, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb, or Bi) in specific ratios. This composite approach allows the material to achieve both high residual flux density and sufficient coercivity through synergistic effects, eliminating the need for heavy rare-earth elements
2Quantity of substance
If the R content is lowered to increase the proportion of R2Fe14B phase, then the residual flux density increases, but the sinterability decreases and abnormal grain growth occurs
Solution Approach 1:
The invention modifies the compositional parameters by maintaining R content at 10-15 wt% while adding specific transition metals (Co, Ni, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb, or Bi) at 0.01-5.0 wt%. This parameter adjustment enables achieving high Br through enhanced phase composition while maintaining adequate R content to ensure proper sinterability and prevent abnormal grain growth
Solution Approach 2:
The added transition metals (Co, Ni, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb, or Bi) act as intermediary elements that mediate between the R2Fe14B phase and the matrix. These intermediaries enhance the magnetic properties and facilitate sintering processes, allowing high Br to be achieved without compromising sinterability or causing abnormal grain growth
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 optimized R-Fe-B-type sintered magnets exhibit both high Br and stable HcJ, overcoming the limitations of previous methods by ensuring compatibility and productivity, with improved magnetic properties and resource efficiency.
Implementation Method 1
a main phase composed of an R 2 Fe 14 B intermetallic compound
Implementation Method 2
in the R-Fe-B-type sintered magnet sintering step where densification accompanied by liquid phase formation arises
Data Source
AI summary
The purpose of the present invention is to achieve both of a high remanent magnetic flux density and high coercivity which have been heretofore believed to be ambivalent properties to each other. Provided is an R-Fe-B-based sintered magnet which has a composition comprising R (wherein R represents at least one element selected from rare earth elements, and essentially contains Nd), B, M (wherein M represents at least one element selected from Si, Al, Mn, Ni, Co, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi), X (wherein X represents at least one element selected from Ti, Zr, Hf, Nb, V and Ta) and C, with a remainder comprising Fe, O and unavoidable impurities, and has a main phase comprising R2Fe14B and a grain boundary phase comprising an R-C phase having a higher R concentration and a higher C concentration than those in the main phase, the R-Fe-B-based sintered magnet being characterized in that the area ratio of the R-C phase in a cross section of the magnet is more than 0% and 0.5% or less.