Nanocomposite Nd-Y-Fe-B-Mo bulk magnets prepared by injection casting technique

Abstract

The phase composition, magnetic and microstructural properties of Nd2Fe14B/(α-Fe, Fe3B) nanocomposite magnets produced by injection casting technique have been studied. Magnetic hysteresis loop of the Nd7Y6Fe61B22Mo4 permanent magnet demonstrates the coercivity as high as 1289kA/m. Electron microscopy elucidates a microstructure composed of magnetically soft α-Fe, Fe3B and hard Nd2Fe14B/Y2Fe14B nanograins (20–50nm) separated by ultra-thin grain boundary layer. The Henkel plot curve of the Nd7Y6Fe61B22Mo4 magnet yields the existence of exchange coupling interactions between soft and hard phases. Macroscopically large size sheet magnet is obtained due to high glass forming ability of the Nd7Y6Fe61B22Mo4 alloy derived from large atomic radius mismatch and negative enthalpy of alloy constituent elements. The high coercivity of the magnet is attributed to the magnetically hard phase increment, nucleation of reverse domains and the presence of thin grain boundary phase. Good magnetic properties such as remanence of 0.51T, coercivity of 1289kA/m and maximum energy product of 46.2kJ/m3 are obtained in directly casted Nd7Y6Fe61B22Mo4 sheet magnets.