Phase equilibria in the Ni–Mn–In alloy system

Phase equilibria at 700 and 850 °C, critical temperatures of B2/L21 order–disorder transformation and martensitic and ferromagnetic phase regions at room temperature in the Ni–Mn–In system were determined mainly by diffusion triple method using a two-stage diffusion couple technique. It was confirmed that a single phase region of the β phase at both 700 and 850 °C exists in a wide composition range along the NiMn–NiIn section and that the L21 ordered phase region appears in the vicinity of Ni2MnIn in the temperature region below about 800 °C. The composition lines, iso-Ms and iso-TFM, possessing the Ms and TC temperatures at room temperature, respectively, were successfully estimated and the coincidence between the iso-Ms and iso-TFM was confirmed in the composition region from 10 to 20 at.% In in the β-phase region.

► Isothermal phase diagrams at 700 and 850 °C in the Ni–Mn–In ternary system have been established.
► A novel ternary compound, Mn3Ni2In, has been found at 700 °C and identified as the Mn3Ni2Si-type structure.
► The existing composition ranges of martensitic and ferromagnetic phases at room temperature have been determined.
► The existing composition range of the L21 ordered phase at 700 °C has been determined.