Magnetic properties of Sm : (Co,Cu) alloys. I. Electron microscopy

Abstract

The effect of aging on the microstructures of Sm‐Co‐Cu alloys is reported. It is shown that small precipitates are present within the SmCo₅‐type phase in as‐cast material. On aging below 650 °C these precipitates are exceptionally stable, but at 800 °C they coarsen rapidly. These results are rationalized in terms of a coherent precipitate phase boundary. Macroscopic regions of the Sm₂Co₁₇‐type phase contain twins and antiphase domain boundaries. The density of these defects is considerably altered by heat treatment. The observed structures are related to the magnetic properties of the alloys concerned, and in Part II a theory is developed to explain the coercivity mechanisms.