R-T-B Rare Earth Magnet Strengthening via Zr-Rich Grain Boundaries
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Solution Overview
Problem
R-T-B rare earth permanent magnets exhibit poor mechanical properties due to their brittle nature, complex intermetallic compound structure, and inhomogeneous microstructure, which restricts their application in high-stress environments.
Innovation Solution
A high-strength R-T-B rare earth permanent magnet is developed by adding Zr to the raw materials, adjusting the Zr to B and T ratio, and employing a process involving hydrogen decrepitation, jet milling, oriented compression, isostatic pressing, vacuum sintering, and aging treatment to control the morphology, size, and distribution of Zr compounds within the magnet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the main phase grains are refined to improve mechanical properties, then bending strength increases, but magnetic properties are affected
Solution Approach 1:
The patent applies local quality by introducing Zr compounds specifically into the R-rich intergranular phases rather than uniformly throughout the material. This localized addition strengthens the grain boundary regions without affecting the main phase grains, thereby improving mechanical properties while preserving magnetic properties.
Solution Approach 2:
The patent employs preliminary action by adding Zr to the raw materials before the sintering process. This allows the Zr to be incorporated into the R-rich intergranular phases during the initial casting and sintering stages, establishing the strengthening structure before final magnetic property optimization occurs during aging treatment.
2Strength
If Zr compounds are added to strengthen R-rich intergranular phases, then mechanical properties improve, but inhomogeneous distribution may occur
Solution Approach 1:
The patent applies parameter changes by carefully controlling the Zr content within a specific range (0.1-1.0 wt%) and adjusting sintering parameters (temperature 1000-1150°C, time 2-10 hours, atmosphere composition) to optimize the precipitation and distribution of Zr compounds. These parameter optimizations ensure homogeneous distribution while achieving the desired strengthening effect.
3Strength
If conventional binary alloy sintering method is used to add second-phase particles, then mechanical properties can be improved, but impurities are easily introduced
Solution Approach 1:
The patent applies the taking out principle by removing the need for external second-phase particles from the conventional binary alloy sintering method. Instead of adding separate particles, the Zr is incorporated into the raw materials and precipitates in-situ within the R-rich intergranular phases during sintering, eliminating the risk of impurity introduction from external additives.
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 method effectively strengthens the R-rich intergranular phases, improving the mechanical properties of the magnet by enhancing its bending strength and maintaining the coercivity and magnetic properties.
Implementation Method 1
The element Zr in the cast strip will be precipitated in a form of fibrous Zr compounds out of R-rich phases after high-temperature treatment
Implementation Method 2
The cast strip is treated in argon gas at a high temperature of 900-1030° C. and a pressure of 30-50 kPa for 30 minutes to 4 hours
Implementation Method 3
hydrogen decrepitation
Implementation Method 4
jet milling, jet milling for powder particle size distribution optimization
Implementation Method 5
vacuum sintering
Implementation Method 6
vacuum sintering
Implementation Method 7
aging treatment
Data Source
AI summary
The present invention discloses a high-strength R-T-B rare earth permanent magnet and a preparation method thereof. The magnet contains 0.3-1.5 wt. % of an element Zr, and a cast strip prepared through vacuum induction melting and melt spinning is treated at a high temperature to make the element Zr therein precipitate in a form of fibrous Zr compounds from R-rich phases, and the fibrous Zr compounds can be uniformly mixed with magnetic powder after hydrogen decrepitation and powder jet milling and mixing, and gradually grow into rod-like Zr compounds existing in the R-rich intergranular phases during the sintering of a green compact. By adjusting the content of the element Zr, sintering temperature and time and other process parameters, the morphology, size and distribution of Zr compounds can be effectively controlled, and the mechanical properties of the magnet can be improved by strengthening the R-rich intergranular phases without deteriorating the magnetic properties of the magnet.