Abstract
Additive manufacturing (AM) allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) – to fabricate isotropic near-net-shape Nd-Fe-B bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic Nd-Fe-B powder and 35 vol% polyamide (Nylon-12). The density of the final magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: Intrinsic coercivity Hci = 8.65 kOe, Remanence Br = 5.07 kG, and energy product (BH)max = 5.47 MGOe (43.50 kJ/m3). The temperature dependence of the magnetic properties in the final magnet products is similar to that of the starting material, indicating that the BAAM process did not degrade the magnetic properties. In addition, tension tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18 %. Scanning electron microscopy images indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binders. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.
