[P1] RE-Fe-B Magnets

[P1-20] Potential of Cryogenic Treatment Applications on Rare-Earth-Based Functional Magnetic Materials

*Rafael Gitti Tortoretto Fim¹, Matic Jovičevič-Klug¹, Dierk Raabe², Patricia Jovičevič-Klug³ (1. Sustainable Magnets and Recycling Group, Physics of Microstructure and Alloy Design Department, Max-Planck-Institute for Sustainable Materials (MPI-SusMat),Düsseldorf (Germany), 2. Physics of Microstructure and Alloy Design Department, Max-Planck-Institute for Sustainable Materials (MPI-SusMat), Düsseldorf (Germany), 3. Surface Science for Future Materials Group, Department of Interface Chemistry and Surface Engineering, Max-Planck-Institute for Sustainable Materials (MPI-SusMat), Düsseldorf (Germany))

Keywords:

Cryogenic treatment,Functional materials,Rare earth permanent magnets,Sustainability

Rare-earth (REs)-based permanent magnets are one of the classes of functional materials that are essential for low carbon energy technologies, such as green energy applications (i.e. wind energy) and fossil-fuel-free mobility (i.e. electromobility). Among all the hard magnetic materials used in industry, Nd-Fe-B permanent magnets stand out as the magnet of choice for many applications due to its unique combination of properties, such as elevated extrinsic magnetic properties, thermal resistance, suitable mechanical properties, and high corrosion resistance. Typically, the improvement of such properties can be achieved through chemical composition manipulation and the use of alloying elements, tailoring of microstructure via thermo-mechanical processes and the use of coatings, in that order. Recent studies have focused on the post-processing that can be cost-effective, relatively easy to apply, sustainable in terms of resource(s) consumption, and that can simultaneously improve/manipulate various properties of such functional materials. In recent years, cryogenic treatment (CT) has been widely used as a multi-property tailoring process for different ferrous and non-ferrous alloys, including microstructural, structural and surface properties modification. During CT material is subjected to sub-zero temperatures for a certain period of time. There are known 3 different types of CT, first is so-called conventional CT (CCT in the range 273-193 K), second is shallow CT (SCT is in the range of 193-113 K) and third is deep CT (DCT is below 113 K). Ferrous and non-ferrous alloys subjected to such cryogenic treatments exhibited improvements on mechano-chemical-physical behavior, corrosion and wear resistance through microstructural changes, such as increased precipitation of carbides, grain morphology alteration and lattice strain alterations. Based on this, we explore and demonstrate the potential of applying DCT as a cost-effective and sustainable multi-property manipulation process for Nd-Fe-B based permanent magnets, aimed particularly at manipulating the extrinsic magnetic properties and corrosion resistance of the entire material.