Effect of Al, Cu, Ga, and Nb additions on the magnetic properties and microstructural features of sintered NdFeB

Abstract

This study describes the relative effect on the permanent magnet characteristics viz. remanence (Br), intrinsic coercivity (Hci), Curie temperature (TC), and rectangularity of the intrinsic demagnetization curve, when Al, Cu, Ga, and Nb are added individually to NdFeB. Each elemental addition causes significant improvement in Hci but the level of improvement differs from one additive element to the other. The addition of Nb is favored over other elements for realizing maximum enhancement in Hci and rectangularity of the demagnetization curve. The microstructural features of the sintered samples of NdFeB with elemental addition show the formation of a new phase, in addition to the phases (φ,η, and Nd-rich) generally found in the ternary sample. The factors influencing the permanent magnet characteristics of sintered samples are the distribution of the Nd-rich phase in the intergranular region, the size and distribution of the minor phases at the grain junctions, the formation and distribution of new phases due to alloying addition, and the solubility of the dopant element in various phases coexisting in the sample.

Microstructure and Mössbauer studies on magnetostrictive Tb0.3Dy0.7Fe1.95 − x Nb x (x = 0, 0.025, 0.05 and 0.075)

“…Consequently, the magnetostrictive RFe 2 phase fraction is reduced, diluting the transduction properties. In the analogous Nd-Fe-B and Sm-Fe systems, it has been widely reported that the permanent magnetic properties are affected by the presence of free iron, which is the primary phase formed under normal solidification conditions [4][5][6]. The studies reported indicate that Nb addition is effective in scavenging the free iron.…”

Crystallization behaviour and high coercivity of (Nd,Pr)13Fe80Nb1B6 melt-spun ribbons

“…Partly substituting Pr for Nd leads to relatively high coercivity of Nd-Fe-B magnets [3,5] because Pr 2 Fe 14 B has a higher anisotropic field than Nd 2 Fe 14 B [6]. The addition of Nb, in both the traditional powder sintered Nd-Fe-B magnets and Nd 2 Fe 14 B-based melt-spun ribbons, can suppress α-Fe precipitation, form a Nb-Fe-B intergranular phase [7][8][9], and/or serve as the solute atom in Nd 2 Fe 14 B grains and refine the grain size during the crystallization process [2,10]. For instance, the average grain sizes of the Nd 12 Fe 82−x B 6 Nb x (x = 0, 1.5) melt-spun ribbons are 22.5 and 15.0 nm, respectively [10].…”

Structure and Properties of Nd-Fe-B Alloy Subjected to HDDR Process

“…It is believed, that neodymium magnets, besides components made of noble metals, are one of the most interesting group of electronic waste to be recycled. Their chemical composition is based on the rare earth elements [2][3][4], like neodymium (Nd), dysprosium (Dy) or praseodymium (Pr), which are now considered by the European Commission to be the critical ones [5]. Furthermore, development of new green technologies, such as aerogenerators or electric enginesindustries, is controlled by rare earth supply [6].…”