Thermal properties and glass-forming ability of bulk glassy alloys

众所周知，pd基和zr基玻璃合金具有玻璃化转变和广泛的过冷液体区域。这些大块非晶合金使我们能够研究这些合金的热性能和电阻率。本工作的主要目的是在所得数值的基础上讨论这些合金的非晶形成能力。用激光闪蒸技术测量了合金的热扩散系数。电阻率测量采用直流四探头技术。比热是用热流型差示扫描量热计测量的。合金在液态时的热扩散系数可归纳为与温度正相关的线性方程。液相温度下合金的热扩散系数越低，获得非晶合金的临界冷却速率越低。因此，合金液体的热扩散系数值可能是其玻璃形成能力的一个指标。Zr_<55>Al_<10>Ni_5Cu_<30>合金的热扩散系数值在玻璃态表现出正的温度依赖关系。合金的热扩散系数在结晶温度（Tc）处急剧增大。在结晶温度范围内，随着温度的升高，热扩散系数逐渐增大，表现为三个阶段。电阻率值在Tc处突然减小，并逐渐减小，表现出与热扩散率值相同的趋势。玻璃态Zr_<55>Al_<10>Ni_5Cu_<30>的比值为0.372 Jg^<-1>K^<-1>。得到了液态钯基合金的比热值。这些值显示出很小的负温度依赖性。用Wiedemann Franz定律分析表明，pd基合金在过冷液态和液态下的主要机理可能是由电子控制。

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.