Experimental study of the Mn–Re system

•Experimental characterization of the Mn–Re phase diagram between 800 and 1150°C.•σ and χ Frank–Kasper phases present very extended solubility domains in this system.•Re has a strong preference for atomic sites with high CN in Frank–Kasper phases.•σ phase molar enthalpy of formation was measured by drop calorimetry at 1150°C. Rhenium (Re) is used as an alloying element in Ni based superalloys but promotes the formation of fragile intermetallic compounds in many systems. The thermodynamic databases that allow the modeling of the properties of Ni based alloys are still incomplete and further data has to be integrated. In this context, we propose a new characterization of the system Mn–Re for temperatures below 1150°C. We evidenced the existence of σ and χ (αMn) Frank–Kasper phases with very large solubility domains. We took a peculiar attention to the atom distribution in both phases and structural analyses (Rietveld refinement) reveal that Re has a strong preference for atomic sites with high CN. In addition, σ phase molar enthalpy of formation was measured by drop calorimetry at 1150°C (40 and 55at.% Re).