Investigation of the enthalpy/entropy variation and structure of Ni–Mn–Sn (Co, In) melt-spun alloys

Abstract

The effect of In and Co additions on the structure and thermal properties of melt-spun process Ni–Mn–Sn alloys has experimentally investigated at a solidification rate of ~48 m s−1. The present study reports on the analysis of the microstructure, martensitic transformation of Ni50Mn42.5Sn7.5, Ni50Mn37.5Sn7.5Co5 and Ni50Mn37Sn6.5In6.5. Heusler alloys produced by melt spinning. The crystal structures of the fabricated alloys were determined by means of X-ray diffraction. While the as-spun alloy Ni50Mn42.5Sn7.5 displayed a single-phase (14M monoclinic martensite) structure at room temperature, the as-spun Ni50Mn37.5Sn7.5Co5 displayed a main martensitic phase of a four-layered orthorhombic (4O) structure and the as-spun Ni50Mn37Sn6.5In6.5 displayed a single-phase cubic Heusler L21. The characteristic transformation temperatures and the thermodynamic parameters of the samples were determined by differential scanning calorimetry measurements. This study investigated the effect of the substitution of Co by Mn in Ni50Mn42.5−xSn7.5Cox. The martensitic transformation temperatures, enthalpy and entropy changes were found to increase progressively with doping Co content and the effect of the substitution of In by Mn. The martensitic transformation temperatures, enthalpy and entropy changes were found to decrease progressively with doping In.