Microstructural and fractographic study of the Ni50Mn50 alloy after low-temperature long-term aging

Abstract

Recently, interest has arisen in alloys based on the NiMn binary system as alloys with magnetically controlled thermoelastic transformation, and therefore magnetically controlled shape memory effects, due to which they can be used as solid-state coolant elements [1, 2]. Films based on the antiferromagnetic alloy NiMn [3 - 6] are also being studied, since they have high potential for practical application in the field of spintronics. [7 - 11]. The microstructure of a binary equiatomic alloy of nominal composition Ni50Mn50 after long-term storage at room temperature is investigated. It has been established that phase stratification occurs in the alloy caused by the disintegration of the lamellar martensitic structure with the formation of micro- and nanoscale regions. A fractographic analysis of the fractures of the samples of the alloy under study was carried out. It was found that in the initial state (homogenizing annealing and quenching), the nature of the fractures is brittle. The fracture after aging is not only fragile in nature, but there are also viscous areas corresponding to the disintegrated parts. The microhardness of the alloy in two states was measured. The microhardness of the martensite alloy decreases by about 25% after aging. The microstructure of the Ni50Mn50 alloy was studied by scanning electron microscopy (SEM).