Structure and magnetic properties of bulk isotropic and anisotropic Nd2Fe14B∕α-Fe nanocomposite permanent magnets with different α-Fe contents

Abstract

Chemical coating, hot compaction, and hot deformation techniques have been applied to prepare bulk isotropic and anisotropic Nd2Fe14B∕α-Fe nanocomposite magnets. The effect of α-Fe content on the structure and magnetic properties of the magnets were studied. For the isotropic magnets, the remanence (Br) increases as the α-Fe content increases, while the coercive force (Hci) drops simultaneously. For the anisotropic magnets, the Br rises first, peaking at 2vol% of α-Fe content, then falls as the α-Fe content increases, and Hci drops significantly for all the α-Fe containing anisotropic magnets. Crystal structure analysis shows that only the magnets with no more than 2vol% α-Fe exhibit strong c-axis crystal texture of Nd2Fe14B phase after deformation. Microstructure observation also shows that there are many Nd2Fe14B equiaxial grains even after hot deformation in the magnets with α-Fe more than 2vol%.

Structure and magnetic properties of bulk anisotropic SmCo5/α-Fe nanocomposite permanent magnets prepared via a bottom up approach

“…The resultant slurry was ultrasonically vibrated with heptane solvent and settled down for 10 min, during which the nanoflakes sediment were separated from the small nanoparticles [6][7][8]. The flakes were then coated with iron nanoparticles by sono-chemical method [9], and the nominal a-Fe content was 0-10 wt.%. The hybrid SmCo 5 /a-Fe powers were magnetically aligned and then sintered at 650°C for 5 min under 300 MPa by spark plasma sintering method.…”

Investigation on magnetic properties of orientated nanocomposite Pr2Fe14B/α-Fe permanent magnets by micromagnetic finite-element method

“…Many studies show that R-rich grain-boundary phase is critical to obtain desired crystallographic texture and therefore R 2 Fe 14 B texture usually appears in R-rich alloys [9,10]. Recently, preferential growth of R 2 Fe 14 B nanocrystals was realized in R-lean alloys by employing a high-pressure technology [11][12][13][14]. It should be noted that R 2 Fe 14 B grains were only partially aligned in experimental study.…”

“…Furthermore, the amount of a-Fe is limited to be lower than 2% vol. because more a-Fe will lead to deterioration of R 2 Fe 14 B crystallographic texture [14]. Control over crystallite orientation of hard phase grains in exchange-coupled magnets is still a challenge to experimentalists.…”

Die-upset Nd11.5Fe72.4Co9Nb1B6.1 magnets with additions of Zn, Al and Sn

“…Die-upset Nd-Fe-B magnets have high magnetic properties since Nd 2 Fe 14 B grains oriented in such a way that the c-axis of grains is parallel to the press direction [1][2][3]. A stress-induced preferential grain growth via dissolution and precipitation has been proved as the texture formation mechanism [4].…”