Structure of Alloys for (Sm,Zr)(Co,Cu,Fe)Z Permanent Magnets: First Level of Heterogeneity

Andrey G. Dormidontov,Natalia B. Kolchugina,Nikolay A. Dormidontov,Yury V. Milov

doi:10.3390/ma13173893

Abstract

An original vision for the structural formation of (Sm,Zr)(Co,Cu,Fe)Z alloys, the compositions of which show promise for manufacturing high-coercivity permanent magnets, is reported. Foundations arising from the quantitative analysis of alloy microstructures as the first, coarse, level of heterogeneity are considered. The structure of the alloys, in optical resolutions, is shown to be characterized by three structural phase components, which are denoted as A, B, and C and based on the 1:5, 2:17, and 2:7 phases, respectively. As the chemical composition of alloys changes monotonically, the quantitative relationships of the components A, B, and C vary over wide ranges. In this case, the hysteretic properties of the (Sm,Zr)(Co,Cu,Fe)Z alloys in the high-coercivity state are strictly controlled by the volume fractions of the A and B structural components. Based on quantitative relationships of the A, B, and C structural components for the (R,Zr)(Co,Cu,Fe)Z alloys with R = Gd or Sm, sketches of quasi-ternary sections of the (Co,Cu,Fe)-R-Zr phase diagrams at temperatures of 1160–1190 °C and isopleths for the 2:17–2:7 phase composition range of the (Co,Cu,Fe)–Sm–Zr system were constructed.

Highlights

Permanent magnets based on the (Sm,Zr)(Co,Cu,Fe)Z alloys, which were developed and commercialized a while ago [1,2], are complex metallurgical systems and their hysteretic properties and structural state are closely linked to the chemical composition of the material and heat treatment conditions
Note thatwhich it is difficult to compare the data on the phase diagrams constructed by different investigators, use different coordinate systems
We present here an original view on the issues of the structural formation of the (R,Zr)(Co,Cu,Fe)Z

Summary

Introduction

Permanent magnets based on the (Sm,Zr)(Co,Cu,Fe)Z alloys, which were developed and commercialized a while ago [1,2], are complex metallurgical systems and their hysteretic properties and structural state are closely linked to the chemical composition of the material and heat treatment conditions. Despite numerous investigations into the structural formation and properties of the alloys, the studies are far from over. The phase composition of boundaries between cells at different states of heat treatments [3,4,5,6] meets with strongly conflicting views. Popov et al [7] assume that the boundary phase is separated so that Cu is localized in the 1:5 phase near the (1:5)/(2:17) interface rather than in the center of the

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