A surface treatment method for a hydrogen absorbing alloy powder of the present disclosure is used for a surface treatment on a hydrogen absorbing alloy powder containing rare earth elements and nickel as constituent elements, including an immersion process in which the hydrogen absorbing alloy powder is immersed in an aqueous alkaline solution; and a removal process in which a liquid containing the hydrogen absorbing alloy powder immersed in the aqueous alkaline solution is introduced into a liquid cyclone, and undesired substances having a smaller specific gravity than the hydrogen absorbing alloy powder adhered to the surface of the hydrogen absorbing alloy powder are removed.

A preparation method of a rare earth permanent magnetic material comprises one or more times of cryogenic treatment and tempering treatment. When the preparation method comprises one time of cryogenic treatment and tempering treatment, the cryogenic treatment is performed between sintering treatment and the tempering treatment, or is performed after the tempering treatment. When the preparation method comprises two or more times of cryogenic treatment and tempering treatment, at least one time of cryogenic treatment is performed between sintering treatment and the tempering treatment, and at least one time of cryogenic treatment is performed after the tempering treatment. The preparation method can refine and homogenize the structure and realize quick and convenient treatment, and can effectively improve the mechanical performance of the rare earth permanent magnetic material and maintain good magnetic performance.

Disclosed are a nickel-based superalloy formed by selective laser melting and a preparation method thereof. In the method, CrFeNb alloy powder is used as a grain refiner, and its element composition is within the composition range of a nickel-based superalloy powder to ensure that the prepared nickel-based superalloy has the same element composition with the original alloy; the grain size in the nickel-based superalloy could be refined by the addition of CrFeNb alloy powder, such that the anisotropic columnar grain structure in the alloy is transformed to equiaxed grain structure, thereby improving mechanical properties of the alloy.

New types of particle feedstocks and heterogeneous grain structures are provided for rare earth permanent magnets (REPMs) and their production in a manner to significantly enhance toughness of the magnet with little or no sacrifice in the hard magnetic properties. The novel tough REPMs made from the feedstock have heterogeneous grain structures, such as bi-modal, tri-modal, multi-modal, laminated, gridded, gradient fine/coarse grain structures, or other microstructural heterogeneity and configurations, without changing the chemical compositions of magnets.

A sintered magnet body (R.sub.aT.sup.1.sub.bM.sub.cB.sub.d) coated with a powder mixture of an intermetallic compound (R.sup.1.sub.iM.sup.1.sub.j, R.sup.1.sub.xT.sup.2.sub.yM.sup.1.sub.z, R.sup.1.sub.iM.sup.1.sub.jH.sub.k), alloy (M.sup.1.sub.dM.sup.2.sub.e) or metal (M.sup.1) powder and a rare earth (R.sup.2) oxide is diffusion treated. The R.sup.2 oxide is partially reduced during the diffusion treatment, so a significant amount of R.sup.2 can be introduced near interfaces of primary phase grains within the magnet through the passages in the form of grain boundaries. The coercive force is increased while minimizing a decline of remanence.

Provided is a color encoding method including providing a composition including a liquid medium and magnetic nanoparticles dispersed in the liquid medium; applying a magnetic field to the composition to align the magnetic nanoparticles; and applying a patterned energy source to the composition to solidify the composition, wherein more than one region of the composition are sequentially solidified with varying magnetic field strength to fix a plurality of color codes.

Provided is a color encoding method including providing a composition including a liquid medium and magnetic nanoparticles dispersed in the liquid medium; applying a magnetic field to the composition to align the magnetic nanoparticles; and applying a patterned energy source to the composition to solidify the composition, wherein more than one region of the composition are sequentially solidified with varying magnetic field strength to fix a plurality of color codes.

New types of particle feedstocks and heterogeneous grain structures are provided for rare earth permanent magnets (REPMs) and their production in a manner to significantly enhance toughness of the magnet with little or no sacrifice in the hard magnetic properties. The novel tough REPMs made from the feedstock have heterogeneous grain structures, such as bi-modal, tri-modal, multi-modal, laminated, gridded, gradient fine/coarse grain structures, or other microstructural heterogeneity and configurations, without changing the chemical compositions of magnets.

Provided is a color encoding method including providing a composition including a liquid medium and magnetic nanoparticles dispersed in the liquid medium; applying a magnetic field to the composition to align the magnetic nanoparticles; and applying a patterned energy source to the composition to solidify the composition, wherein more than one region of the composition are sequentially solidified with varying magnetic field strength to fix a plurality of color codes.

Provided is a color encoding method including providing a composition including a liquid medium and magnetic nanoparticles dispersed in the liquid medium; applying a magnetic field to the composition to align the magnetic nanoparticles; and applying a patterned energy source to the composition to solidify the composition, wherein more than one region of the composition are sequentially solidified with varying magnetic field strength to fix a plurality of color codes.