ThMn12 Rare Earth Sintered Magnet With Oxycarbide Grain Boundaries
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Solution Overview
Problem
Existing methods struggle to achieve a high sintered density of 95% or more in sintered magnets with a ThMn12-type crystal compound, leading to unfavorable magnetic characteristics and temporal degradation.
Innovation Solution
Incorporating an Sm-containing oxycarbide in the sintering process to form an anisotropic rare earth sintered magnet with a ThMn12-type crystal compound, utilizing a composition that includes R oxycarbide in the grain boundary area and specific phases to enhance sintered density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a ThMn12-type crystal compound is used as the main phase to reduce rare earth content, then rare earth consumption is reduced and magnetic characteristics are improved, but sintered density cannot be achieved at 95% or more leading to temporal degradation
Solution Approach 1:
The invention changes the chemical composition parameters by introducing specific interlattice intruding atoms (C, N, O) into the ThMn12-type crystal structure and forming R-rich phases at grain boundaries. This compositional modification enables achieving 95% or more sintered density while maintaining low rare earth content, thereby resolving the contradiction between reducing rare earth consumption and ensuring temporal stability.
Solution Approach 2:
The invention creates a composite microstructure consisting of ThMn12-type main phase grains with interlattice intruding atoms and R-rich phase grain boundary regions. This composite structure combines the low rare earth content advantage of ThMn12 with the high density and stability provided by the R-rich grain boundary phases, resolving the contradiction between rare earth reduction and temporal stability.
2Ease of manufacture
If conventional sintering methods are used for ThMn12-type magnets, then production process is simple, but sintered density remains below 95% causing unfavorable magnetic characteristics
Solution Approach 1:
The invention modifies the chemical composition parameters (adding C, N, O interlattice intruding atoms and controlling R-rich phase formation) to enable achieving 95% or more sintered density through conventional sintering processes, thereby improving manufacturing precision without complicating the manufacturing process.
3Reliability
If element X is introduced into interstitial sites to improve Curie temperature and magnetic anisotropy, then magnetic properties are enhanced, but sintered density still cannot reach 95% or more
Solution Approach 1:
The invention simultaneously optimizes multiple composition parameters: introducing C, N, or O as interlattice intruding atoms to enhance magnetic anisotropy and Curie temperature, while also controlling the formation of R-rich phases at grain boundaries. This multi-parameter optimization achieves both enhanced magnetic properties and 95% or more sintered density.
Solution Approach 2:
The invention creates a composite structure where the ThMn12 main phase contains interlattice intruding atoms for enhanced magnetic properties, while R-rich phases at grain boundaries provide high density. This composite approach simultaneously achieves improved magnetic anisotropy and 95% or more sintered density.
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 solution achieves a sintered density of 7.3 g/cm3 or more, stabilizing magnetic characteristics and preventing temporal degradation, while maintaining good magnetic properties.
Implementation Method 1
sintering and aging it
Implementation Method 2
which contains an R oxycarbide in the grain boundary area
Implementation Method 3
a compound having a ThMn12-type crystal structure has a smaller rare earth content than an R2Fe14B compound and has better magnetic characteristics
Data Source
AI summary
Provided are an anisotropic rare earth sintered magnet having a ThMn12-type crystal compound as a main phase and exhibits good magnetic characteristics, and a method for producing it. The anisotropic rare earth sintered magnet has a composition of a formula (R1-aZra)v(Fe1-bCob)100-v-w-x-y(M11-cM2c)wOxCy (where R is one or more kinds selected from rare earth elements and indispensably includes Sm, M1 is one or more kinds of elements selected from the group consisting of V, Cr, Mn, Ni, Cu, Zn, Ga, Al, and Si, M2 is one or more kinds of elements selected from the group consisting of Ti, Nb, Mo, Hf, Ta, and W, and v, w, x, y, a, b, and c each satisfy 7≤v≤15 at %, 4≤w≤20 at %, 0.2≤x≤4 at %, 0.2≤y≤2 at %, 0≤a≤0.2, 0≤b≤0.5, and 0≤c≤0.9), which contains a main phase of a ThMn12-type crystal compound in an amount of 80% by volume or more with the average crystal particle diameter of the main phase being 1 μm or more, which contains an R oxycarbide in the grain boundary area, and which has a density of 7.3 g/cm3 or more. The production method for the anisotropic rare earth sintered magnet includes grinding an alloy that contains a ThMn12-type crystal compound phase but does not contain an oxycarbide, then molding it in a mode of pressure powder molding with magnetic field application thereto to give a molded article, and thereafter sintering it at a temperature of 800° C. or higher and 1400° C. or lower to form an oxycarbide in the grain boundary area.