【作者】 佟存柱；

【导师】 林德华；

【作者基本信息】 重庆大学 ， 凝聚态物理， 2002， 硕士

【摘要】 本文研究了块体金属玻璃Zr48Nb8Cu12Fe8Be24 的电阻、比热，并通过电阻、比热、超声手段研究了这种金属玻璃的玻璃转变和晶化过程。用水淬方法制备了块体金属玻璃Zr48Nb8Cu12Fe8Be24，并用差示扫描量热（DSC）实验和X射线衍射实验确定合金的非晶本质，发现金属玻璃Zr48Nb8Cu12Fe8Be24有明显的玻璃转变点，高温下存在两次晶化。依据DSC实验选择温度点对样品进行退火处理，XRD实验确定了退火对样品的结构影响，发现两次晶化产物不同。对这些样品进行低温电阻测量，发现金属玻璃Zr48Nb8Cu12Fe8Be24具有负的电阻温度系数，并可以用衍射模型、局域自旋理论解释，随着退火温度的升高，电阻温度系数由负向正逐步过渡。测量了金属玻璃Zr48Nb8Cu12Fe8Be24室温至熔化温度的高温电阻，发现过冷液相区电阻变化明显不同与晶态和非晶态。对块体金属玻璃Zr48Nb8Cu12Fe8Be24及退火样品进行了超声和密度测量实验，发现与晶态相比，非晶态Zr48Nb8Cu12Fe8Be24横波声子发生大幅度软化，同时伴随着杨氏模量、剪切模量、德拜温度、密度、体积模量的降低，而泊松比升高。在过冷液相区，样品表现出所有过冷液体的特征。对块体金属玻璃Zr48Nb8Cu12Fe8Be24及退火样品进行了低温比热测量，发现非晶态和退火样品低温比热在T<20 K范围内均可用德拜模型解释。测量了金属玻璃Zr48Nb8Cu12Fe8Be24及不同晶态样品的交流磁化率与温度关系和在5 K温度下的B-H关系，发现在直到5 K的低温下，晶态和非晶态的Zr48Nb8Cu12Fe8Be24合金依然表现为顺磁性，非晶态的磁化率要略高于晶态的，量级均为10-5。更多还原

【Abstract】 Crystallization and glass transition of the bulk metallic glass Zr48Nb8Cu12Fe8Be24 are investigated by electrical resistance, low-temperature specific heat and ultrasonic measurement. The bulk metallic glass Zr48Nb8Cu12Fe8Be24 was prepared successfully by water quenching method. Amorphous nature of the alloys was confirmed by differential scanning calorimetry (DSC) and x-ray diffraction (XRD) experiments. DSC experiment showed the presence of two crystallization processes for this bulk metallic glass at high temperature. Electrical resistance measurement was performed for the amorphous sample and annealed (at different temperatures) samples by using an usual four-probe method from 4.2 to 280 K in a dc mode. A negative temperature coefficient of resistivity (TCR) is found for the amorphous sample and TCR changes its sign from negative to positive with the increase of annealing temperature. The resistance of the as-prepared sample was also investigated from room temperature to 1000 K. The resistivity of sample decreased largely when the first crystallization occurred, increased when the second crystallization occurred and decreased with the increase of temperature after second crystallization.Density and ultrasonic measurement for the amorphous sample and the annealed samples were performed. A supersoftening of long-wavelength transverse acoustic phonons was found in the amorphous Zr48Nb8Cu12Fe8Be24 sample compared to the crystallized samples, which also accompany with the decrease of Young’s modulus, shear modulus, Debye temperature, density, bulk elasticity modulus, and increase of Peson’s proportion. The samples showed typical properties of supercooled liquid in the supercooled liquid region.Temperature dependence of specific heat for the bulk metallic glass Zr48Nb8Cu12Fe8Be24 and annealed samples were investigated. Specific heat for both amorphous sample and annealed samples may be explained by Debye model. The investigation of magnetic properties showed paramagnetism for both amorphous and crystalline samples at temperature as low as 5 K. The susceptibility (～10-5) for the crystallized sample is lower than the amorphous sample.更多还原