R-T-B-Ga Magnet Alloy Phase Structure for Property Stability
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Solution Overview
Problem
Variations in magnetic properties of Ga-containing R-T-B-based sintered magnets during manufacturing pose a challenge, and there is a need to enhance these properties further.
Innovation Solution
An R-T-B—Ga-based magnet material alloy is developed with a crystal structure comprising an R2T14B phase and an R-rich phase that includes both non-crystalline and crystalline phases, where the non-crystalline phase has a higher Ga content. This alloy is produced through a strip casting method followed by thermal maintenance at 650°C to 900°C and controlled cooling at 1°C to 9°C per second, facilitating the release of impurities into the R-rich phase and optimizing magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ga is added to R-T-B-based alloy to improve coercive force, then magnetic properties are enhanced, but variations in magnetic properties increase during manufacturing
Solution Approach 1:
The patent applies local quality by creating a dual-phase R-rich phase structure where non-crystalline Ga-enriched regions are distributed within crystalline R-rich phase matrices. This local differentiation allows Ga to be concentrated where it provides maximum benefit (grain boundary regions) while the surrounding crystalline phase maintains structural stability, thus enhancing coercive force locally without causing widespread property variations
Solution Approach 2:
The patent creates a composite microstructure by combining non-crystalline and crystalline phases within the R-rich phase region. The non-crystalline phase enriched with Ga forms a composite system with the crystalline R-rich phase, leveraging the benefits of both phases: the non-crystalline phase provides Ga concentration and magnetic property enhancement, while the crystalline phase provides structural stability and reduces manufacturing variations
2Strength
If thermal maintenance is performed at high temperature to optimize microstructure, then magnetic properties are improved, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by optimizing the thermal maintenance temperature range to 650-900°C, which is sufficient to activate atomic diffusion and form the desired non-crystalline/crystalline dual-phase structure without requiring excessively high temperatures. This temperature optimization achieves the required microstructural transformation while minimizing energy consumption compared to conventional high-temperature heat treatments
3Strength
If controlled cooling rate is applied to form non-crystalline phase, then magnetic properties are enhanced, but production time increases
Solution Approach 1:
The patent applies partial action by implementing controlled cooling only during the critical phase transformation window (from thermal maintenance temperature to room temperature), rather than controlling the entire production process timeline. The controlled cooling rate of 1-9°C/s is applied specifically to form the non-crystalline phase and distribute Ga, achieving the required microstructure without unnecessarily extending other production stages
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 resulting sintered magnets exhibit improved coercive force, reduced reverse magnetic domain nucleation, and increased saturation magnetization, stabilizing the magnetic properties and enhancing the energy product.
Implementation Method 1
The molten alloy is supplied, via a tundish, to the outer peripheral surface of a chill roll having a structure in which coolant circulates, and quenched. Thus, the molten alloy is solidified to be cast into a ribbon
Implementation Method 2
they are thermally maintained by being held at a temperature in the range of 650° C. to the melting temperature of the alloy for a predetermined time
Implementation Method 3
after the thermal maintenance, the alloy flakes are cooled at a cooling rate of 1° C. to 9° C. per second
Data Source
AI summary
Disclosed is an R-T-B—Ga-based magnet material ahoy where R is at least one element selected from rare earth metals including Y and excluding Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and T is one or more transition metals with Fe being an essential element. The R-T-B—Ga-based magnet material alloy includes: an R2T14B phase 3 which is a principal phase, and an R-rich phase (1 and 2) which is a phase enriched with the R, wherein a non-crystalline phase 1 in the R-rich phase has a Ga content (mass %) that is higher than a Ga content (mass %) of a crystalline phase 2 in the R-rich phase. With this, it is possible to enhance the magnetic properties of rare earth magnets that are manufactured from the alloy and reduce variations in the magnetic properties thereof.