Metallurgical behavior of Sm(Co,Fe,Cu,Zr)z alloys

Abstract

A model, based on the Sm-Co system between SmCo5 (1:5) and Sm2Co17 (2:17 R and 2:17 H), is proposed to describe the metallurgical behavior of Sm(Co,Fe,Cu,Zr)z alloys between 6.8<z<8.5 in the development of hard magnetic properties. The same phases are encountered in both the binary and multicomponent alloys, but the stability ranges of the 1:5 and 2:17 phases are altered by the additive elements. The following points are made: (1) Cu, and Fe in combination with Cu, extend the high temperature stability of the 2:17 R phase to lower z values; (2) Cu stabilizes the 1:5 phase relative to the 2:7 and 2:17 R phases at low temperatures; (3) low concentrations of Fe (≂5 a/o) stabilize the 2:17 R phase relative to the 1:5 phase and Co-rich solid solutions in the presence of Cu; (4) high concentrations of Fe(>10 a/o) destabilize the 2:17 R phase due to Fe-Fe pairs which preferentially occupy the dumbbell sites (6c in R3̄m); (5) Zr-vacancy pairs stabilize the 2:17 R phase at high Fe concentrations by displacing Fe-Fe pairs at the dumbbell sites; (6) high coercivity permanent magnets of the type Sm(Co,Fe,Cu,Zr)z with 6.8<z<8.5 have a partially disordered 2:17 R structure at the solutionizing temperature, and this structure is retained on quenching to room temperature. On isothermal aging, Cu is rejected from the 2:17 R phase by the formation of the Cu:rich 1-5 boundary phase, and Zr is rejected by the formation of the Zr-rich 2:17 H platelet phase.

Sm(Co, Fe, Cu, Zr)z sintered magnets with a maximum operating temperature of 500°C

“…Fig. 2 shows B r , (BH) max , b H C and H k at room temperature vs. Fe content v. The Sm(Co bal Fe v Cu y Zr x ) z magnets represent a complicated system with four compositional variables (v, x, y, z) and at least five heat-treating variables [7]. The microstructures and magnetic properties of Sm(Co,Fe,Cu,Zr) z magnet significantly depend on the processing parameters and heat treatments.…”

Enhanced coercivity of melt-spun Sm(Co,Fe,Cu,Zr)z ribbons annealed by improved process

“…A Zr-rich lamella phase is also superimposed on the cellular microstructure. The coercivity mechanism has been proved to be domain wall pinning type [3,4]. Recently, melt-spun Sm(Co,Fe,Cu,Zr) z ribbons have been successfully prepared using melt-spinning route, reducing complicated heat treatment to sintered magnets, which would be of great value for a more economical preparation of bonded magnets [5][6][7][8][9][10].…”

Structure and magnetic properties of Sm(Co1−xMx)5 (M = Cu, Ag) alloys

“…The domain walls are pinned at different phase boundaries between the Sm 2 (Co,Fe) 17 matrix, the Sm(Co,Cu) 5-7 boundary phase and the Zr-rich platelet phase [2,3]. The magnetic properties of this precipitated Sm(Co,Cu) [5][6][7] phase are important for the understanding of the magnetization process in these magnets [3,5]. In this work the main emphasis is to investigate the formation of the phases Sm(Co,M) 5-7 (M = Ag, Cr) and their magnetic properties.…”