Thermally stable, cladded permanent magnets, and compositions and methods for making the same

Abstract

The disclosed technology provides a cladded permanent magnet comprising: a core magnet region containing a core magnetic material; and a magnet cladding containing a shell magnetic material comprising (i) a magnetic compound that is chemically the same as the core magnetic material, (ii) one or more rare earth elements, and (iii) metal-containing inoculant nanoparticles, wherein the magnet cladding is disposed on the core magnet region, wherein the magnet cladding has at least 10% higher ambient-temperature magnetic coercivity compared to the core magnet region. The cladded permanent magnet is made via high-throughput laser-based additive manufacturing to optimize the architecture of NdFeB or other magnets, generating site-specific, demagnetization-resistant microstructures. This disclosure teaches a rapid, single-step laser-based process to tailor the easy axis alignment, grain size, and microstructure of a permanent magnet at corners and edges to resist demagnetization.

What is claimed is: 
     
         1 . A cladded permanent magnet comprising:
 (a) a core magnet region containing a core magnetic material; and   (b) a magnet cladding containing a shell magnetic material, wherein said shell magnetic material comprises (i) a magnetic compound that is chemically the same as said core magnetic material, (ii) one or more rare earth elements, and (iii) metal-containing inoculant nanoparticles,   wherein said magnet cladding is disposed on said core magnet region,   wherein said magnet cladding is chemically distinct and physically distinct from said core magnet region, and   wherein said magnet cladding has at least 10% higher ambient-temperature magnetic coercivity compared to said core magnet region, wherein said ambient-temperature magnetic coercivity is measured at 25° C.   
     
     
         2 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding has at least 50% higher ambient-temperature magnetic coercivity compared to said core magnet region. 
     
     
         3 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding has at least 10% higher elevated-temperature magnetic coercivity compared to said core magnet region, wherein said elevated-temperature magnetic coercivity is measured at 150° C. 
     
     
         4 . The cladded permanent magnet of  claim 3 , wherein said magnet cladding has at least 50% higher elevated-temperature magnetic coercivity compared to said core magnet region. 
     
     
         5 . The cladded permanent magnet of  claim 1 , wherein said core magnetic material is selected from the group consisting of NdFeB, DyFeB, SmCo, AlNiCo, MnAl, FeN, Fe 3 O 4 , and combinations thereof. 
     
     
         6 . The cladded permanent magnet of  claim 1 , wherein said one or more rare earth elements are selected from the group consisting of Dy, Tb, Pr, Ce, and Nd. 
     
     
         7 . The cladded permanent magnet of  claim 1 , wherein said one or more rare earth elements are alloyed with Cu in the form of a eutectic mixture. 
     
     
         8 . The cladded permanent magnet of  claim 1 , wherein said metal-containing inoculant nanoparticles are selected from the group consisting of Zr, ZrC, ZrB 2 , ZrH 2 , ZrO 2 , Zr 2 O 3 , and combinations thereof. 
     
     
         9 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is a continuous cladding that forms a shell on all surfaces surrounding said core magnet region. 
     
     
         10 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is a discontinuous cladding that is disposed on one or more edges of said core magnet region. 
     
     
         11 . The cladded permanent magnet of  claim 10 , wherein said one or more edges include a trailing edge of an electric motor. 
     
     
         12 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is a discontinuous cladding that is disposed at one or more corners of said core magnet region. 
     
     
         13 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is a discontinuous cladding that is disposed in one or more vertices within said core magnet region. 
     
     
         14 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is a discontinuous cladding that forms a pattern on said core magnet region. 
     
     
         15 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding has a higher concentration of said one or more rare earth elements compared to said core magnet region. 
     
     
         16 . The cladded permanent magnet of  claim 15 , wherein said one or more rare earth elements are present in said magnet cladding at an average concentration from about 0.1 wt % to about 50 wt %. 
     
     
         17 . The cladded permanent magnet of  claim 16 , wherein said one or more rare earth elements are present in said magnet cladding at an average concentration from about 1 wt % to about 25 wt %. 
     
     
         18 . The cladded permanent magnet of  claim 1 , wherein said one or more rare earth elements are uniformly distributed and concentrated within said magnet cladding. 
     
     
         19 . The cladded permanent magnet of  claim 1 , wherein said one or more rare earth elements have a graded concentration within said magnet cladding. 
     
     
         20 . The cladded permanent magnet of  claim 19 , wherein said one or more rare earth elements are at a maximum concentration at an outer surface of said magnet cladding, and wherein said one or more rare earth elements are at a minimum concentration at an inner surface of said magnet cladding. 
     
     
         21 . The cladded permanent magnet of  claim 1 , wherein said one or more rare earth elements have a non-uniform and pre-programmed concentration within said magnet cladding. 
     
     
         22 . The cladded permanent magnet of  claim 1 , wherein said shell magnetic material is distributed anisotropically in density and depth across said cladded permanent magnet. 
     
     
         23 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is produced by solidifying a melt pool containing a molten form of said one or more rare earth elements and a molten form of said core magnetic material. 
     
     
         24 . The cladded permanent magnet of  claim 1 , wherein said shell magnetic material is preferentially located at grain boundaries within said magnet cladding. 
     
     
         25 . The cladded permanent magnet of  claim 1 , wherein said shell magnetic material is preferentially located within grains within said magnet cladding. 
     
     
         26 . The cladded permanent magnet of  claim 25 , wherein said grains are equiaxed grains. 
     
     
         27 . The cladded permanent magnet of  claim 25 , wherein said grains have a magnetic easy axis that is dictated by a crystallographic texture of said grains. 
     
     
         28 . The cladded permanent magnet of  claim 25 , wherein said grains contain a high-energy-product material surrounded by a thermally stable shell material. 
     
     
         29 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is thermally characterized by a magnetic coercivity at 180° C. of at least 4000 Oe. 
     
     
         30 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is formed from laser-based additive manufacturing on said core magnet region. 
     
     
         31 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding is formed from laser welding on said core magnet region. 
     
     
         32 . The cladded permanent magnet of  claim 1 , wherein said magnet cladding forms a scalloped pattern on said core magnet region. 
     
     
         33 . The cladded permanent magnet of  claim 1 , wherein said cladded permanent magnet has a curved shape. 
     
     
         34 . The cladded permanent magnet of  claim 1 , wherein said cladded permanent magnet has a prismatic shape. 
     
     
         35 . The cladded permanent magnet of  claim 1 , wherein said cladded permanent magnet is present in an electric motor.