Kinetics of the phase separation in Cu–Al–Mn alloys and the influence on martensitic transformations

Abstract

We have determined the shape of the miscibility gap of the Cu–Al–Mn alloy system along the Cu3Al → Mn composition line ((Cu3Al)1 − x Mnx with 0 ⩽ x ⩽ 1) using electrical resistance measurements. Electrical resistance measurements have also been used to study the kinetics of the phase separation that takes place within the miscibility gap. The effect of such a phase separation on the magnetic properties of the system and on the martensitic transition displayed by these alloys has also been analysed. The results obtained show that the phase separation produces an enhancement of the ferromagnetic character of the system as a result of the development of ferromagnetic L21 domains. In addition, the phase separation gives rise to an increase in the transition temperature and to a reduction in the associated entropy change. Both effects are a consequence of the growth of L21 Mn-rich domains that do not transform martensitically.