The constitution of copper-hardened samarium-cobalt permanent magnets

Abstract A study has been made of the constitution of copper-hardened samarium-cobalt alloys lying between SmCo 5 and Sm 2 Co 17 and containing up to 20 at.% copper. It is found that copper exerts a strong influence; the 2:17 phase is repressed in favour of the 1:5 phase with the peritectic line changing to a eutectic trough. The solvus line of the 1:5 phase is displaced towards the 2:17 phase in the composition range studied. SmCu 5 and the 1:5 phase are mutually soluble above the latter's eutectoid transformation temperature, which falls as the copper level increases. Finally, the cobalt solid solution comes into direct equilibrium with a wide range of composition of the 1:5 phase in the ternary alloys (in the region of 800°C).