Thermal properties and glass-forming ability of bulk glassy alloys

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Pd-based and Zr-based glassy alloys are well known to exhibit glass transition with a wide supercooled liquid region. These bulk amorphous alloys allow us to investigate thermal properties and electrical resistivity of these alloys. The main purpose of this work is to discuss the glass-forming ability of these alloys on the basis of the obtained values. The thermal diffusivity values of the alloys were measured with a laser flash technique. The electrical resistivity was measured by a direct current four probe technique. The specific heat was measured by the heat flux type differential scanning calorimeter with a triple cell system. The thermal diffusivity values of the alloys in the liquid state are summarized in the linear equations with positive temperature dependency. The lower the thermal diffusivity values of the alloys at liquidus temperature, the lower the critical cooling rate to obtain amorphous alloy becomes. Thus, the thermal diffusivity values of alloy liquids might be an indicator of their glass forming ability. The thermal diffusivity values of Zr_<55>Al_<10>Ni_5Cu_<30> alloy show positive temperature dependence in the glassy state. The thermal diffusivity values of the alloy increase suddenly at crystallization temperature (Tc). The thermal diffusivity values increase gradually showing three stages in the crystallization temperature range with increasing temperature. The electrical resistivity values suddenly decrease at Tc and gradually decrease showing same tendency of the thermal diffusivity values. The specific value of Zr_<55>Al_<10>Ni_5Cu_<30> in the glass state was measured to be 0.372 Jg^<-1>K^<-1>. The specific heat values for liquid Pd-based alloys were also obtained. These values show small negative temperature dependence. It was also suggested from analysis with Wiedemann Franz law that principal mechanism of Pd-based alloy is likely to be controlled by electron in the super cooled liquid and liquid states.