Thermal stability, crystallization and magnetic properties of Fe-Co-based metallic glasses

The aim of the paper was to investigate thermal stability, crystallization and magnetic properties of Fe-Cobased metallic glasses (MGs). Investigations were carried out on amorphous ribbons with the compositions of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 and [(Fe0.6Co0.3Ni0.1)0.75 B0.2Si 0.05]96Nb4. Thermal properties (liquidus Tl and melting Tm temperatures) of the pre-alloyed ingots upon heating and cooling were analyzed by DTA at a heating/ cooling rate of 0.33 K s-1 under the purified argon atmosphere. The structure of the ribbons was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM) method. Kinetics of the crystallization process was examined by applying differential scanning calorimetry (DSC) method, and experiments performed in thermal analysis involve heating at a constant rates b = 0.17, 0.33 and 0.5 K s-1. Additionally, the conventional crystallization temperature Tx was determined from the normalized isochronal resistivity curves a(T) with heating rate 0.0083 K s-1. a is the temperature coefficient of resistance and a = q-1 dq/dT. The Tx, can be obtained from the condition a = 0 (Stokłosa et al. in J Alloy Compd 509(37):9050–9054, 2011). The saturation magnetization M(T) was measured in situ with heating rates 0.083 K s-1 using magnetic balance (Szewieczek and Lesz in J Mater Process Tech 162–163:254–259, 2005)

Martensitic transformation, magnetic entropy, and adiabatic temperature changes in bulk and ribbon Ni48Mn39.5Sn12.5−xInx (x = 2, 4, 6) metamagnetic shape memory alloys

Martensitic transformation, magnetic entropy, and direct adiabatic temperature changes in Ni48Mn39.5Sn12.5− xInx (x = 2, 4, 6) metamagnetic Heusler bulk and grain-constrained ribbon alloys were studied. All alloys showed a typical L21 structure in austenite and the 4O structure in martensite. Their relative volume contributions changed depending on In content. With increasing In concentration, the martensitic transformation temperature increased, whereas the Curie temperature of austenite decreased. The magnetic entropy change under magnetic field of 5 T attained maximum of 20 J/kgK in the bulk and 14.4 J/kgK in the ribbon alloys with the Ni48Mn39.5Sn8.5In4 nominal composition. The corresponding adiabatic temperature change under 1.7 T yielded 1.3 K for the Ni48Mn39.5Sn8.5In4 bulk alloy. Despite grain confinement, melt spinning was found to stabilize martensite phase. Changes observed were discussed with relation to strengthened covalency imposed by In substitution