Production of Nd-Fe-B permanent magnet with melt spinning method and investigation of their stractural and magnetic properties

In this study, Nd15Fe77B8 hard magnetic alloy powders were produced with melt spinning method and the produced powders were milled with high energy ball milling method under vacuum atmosphere with addition of surface reactant material. The morphologic, microstructural, thermal and magnetic properties of produced powders were investigated. The Nd15Fe77B8 magnetic alloy powders were produced by the copper wheel having different surface properties (smooth and texture) and surface temperatures (20 °C and -5 °C) and the produced powders were milled with various milling times ranging from 90 to 390 minutes. The shapes of produced powders changed with wheel properties. Fiber and flaky shaped powders were produced with smooth surface wheel and spherical shaped powders were produced with the surface textured wheel. The cooling rates of produced powders changed with powder size and with wheel surface temperature. The cooling rate of 5 μm thick flaky shaped powders produced with smooth surface wheel at room temperature and -5 °C surface temperatures were calculated as 4,3x106 and 5,95x106 K/s, respectively. The microstructure of produced powders consisted with different phases such as Nd2Fe14B hard magnetic phase, soft magnetic α-Fe phase and Nd-rich phase. The Curie temperatures and coercivities of produced powders significantly changed with high energy ball milling and the values increased with decreasing powder size. The maximum Curie temperature and coercivity values were obtained as 346 °C and 4,375 kOe for smooth surface wheel with -5 °C surface temperature and with 390 minutes milling time, respectively. Key Words: Nd15Fe77B8 hard magnetic alloy, Melt spinning method, Surfactant-assistant ball milling