Thermophysical Properties of Al-Ni-Co-R (R = Sm, Tb) Alloys in Crystalline and Liquid States

Experimental studies of density and electrical resistivity of Al86Ni6Co2R6 (R = Sm, Tb) alloys are performed in a wide temperature range, which covers crystalline and liquid states. Density is measured by gamma absorption method, and electrical resistivity is determined by contact-less method in rotating magnetic field. The liquidus and solidus temperatures, thermal expansion coefficients, and relative changes of density and electrical resistivity upon melting are determined. The molar volumes of the alloys are calculated. It was found that the alloys are characterized by a wide two-phase zone where density and resistivity show nonlinear behavior. At liquidus temperature, a steplike increase in density and decrease of electrical resistivity are found. It has been established that terbium increases density of the alloys and reduces their resistivity more than samarium. In liquid state at T <= 1300-1350 K, density hysteresis is found; no hysteresis is found in temperature dependences of electrical resistivity. This fact can indicate the decomposition of large-scale inhomogeneities, which do not affect the electron subsystem parameters but play an important role in amorphization. The revealed features of the properties will make it possible to optimize the process of melts preparing before rapid quenching in order to obtain high-quality amorphous and nanocrystalline samples.