Mechanosynthesis formation study and electrical resistivity of short milled Fe50Mn35Sn15 Heusler intermetallic compound

Abstract

Although the Heusler alloys are usually obtained by arc melting, in this study we choose to investigate the formation of the off stoichiometric Fe₅₀Mn₃₅Sn₁₅ (at. %) Heusler alloy by mechanical alloying using elemental powders as raw materials. The mechanical alloying was conducted in high-purity argon gas up to 30 h, using a planetary ball mill. The formation by mechanical alloying can be described as complex one, with the formation of the A₂ disordered Heusler phase as the majority phase after 15 h of milling. Milling the alloy up to 30 h, led to Heusler phase decomposition. The phase formation and obtained quantities were analysed using the Rietveld method applied to the recorded X-ray diffraction patterns. Evolution of the mean crystalline size and lattice strain versus milling time were computed. After 30 h of milling, the mean crystallite size of the milled alloy reached a value of 50 nm. The morphology and element distribution were analysed by scanning electron microscopy and energy dispersive X-ray spectroscopy. Particle size distribution showed important changes upon elements reaction, as the elements react, the median particle size (D50) decreases up to 3.5 μm and further increases at 5 μm as the main phase is the A₂ Heusler phase. The electrical resistivity was investigated, and an evolution with phase formation was found, as the electrical resistivity increased up 5.83mΩm at 10 h where an equilibrium between initial elements and Ni2MnSn Heusler phase is found, followed by a sharp decrease up to 2.8 mΩm for 30 h of milling as the Heusler phase is the main phase.