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Direct studies of the adiabatic temperature change (ΔTad) in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni47Mn40Sn12.5Cu0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254–283 K temperature range as well as a second order phase transition near the Curie temperature TC = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value ΔTad = −12 K in 20 T at the initial temperature T0 = 275 K. The irreversible part of the MCE reached ΔTir = −10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems. [ABSTRACT FROM AUTHOR]

This study is devoted to ab initio calculations of the ground state properties of the Mn2NiGa Heusler alloy in the austenitic and martensitic phases. The calculations were performed using an approach in which exchange correlation effects are taken into account via the generalized and metageneralized gradient approximations. The martensitic phase includes four low symmetry structures: the tetragonal unmodulated and three-, five-, and seven-layer modulated monoclinic structures. It is shown that both approximations predict the martensitic transformation between the cubic austenitic and unmodulated martensitic phases, as well as the presence of modulated structures in the martensitic phase. However, the considered approximations lead to opposite behaviors of the energy of the structures and the modulation amplitude with an increase in the modulation period. Namely, these characteristics increase within the generalized gradient approximation and decrease within the metageneralized gradient approximation. [ABSTRACT FROM AUTHOR]

The influence of the conditions of complete and incomplete postwelding annealing on the strength properties of the welded joints of a VT41 alloy is studied. These annealing conditions are developed for the ring welded joints of a VT41 alloy. The optimum conditions are determined for the production of large welded joints of a VT41 alloy for a high-pressure compressor in an advanced engine. The mechanical properties of the base and weld metals are compared after complete and incomplete postwelding annealing. The microstructure of the welded joints after heat treatment is investigated. [ABSTRACT FROM AUTHOR]

The conditions of electron-beam welding (EBW) of ring samples made of a VT41 alloy are adjusted to produce large welded joints of this alloy for a high-pressure compressor (HPC) of an advanced engine. The problems of quality control of a welded joint, the level of residual stresses in the near-weld zone, the microstructure of the welded joint, and its properties are considered. [ABSTRACT FROM AUTHOR]