7.2.1.5.3.1 Introduction

This chapter provides an introduction to the discussion on Fe-Cr-Co base magnet alloys. This alloy system has an α (bcc) phase at high temperatures and it decomposes into two bcc phases, α₁+ α₂, as the result of a suitable heat treatment. Since the α₁ phase is rich in Fe and Co, it is ferromagnetic, whereas the α₂phase is rich in Cr and is non-magnetic. This system is therefore potentially a basis for high-quality permanent magnets, similar to the Fe-Ni-Al base alloys and the Fe-Cr-Co magnets are ductile. The conventional magnet preparation technique consists in general of several steps including a homogenization process at about 900-1000°C of the cast specimen, thermomagnetic or deformation heat treatment at ≈ 650°C followed by some type of aging procedure at lower temperatures.