Zr基块状非晶合金室温压缩与动力学特性研究

【作者】 郭秀丽；

【导师】 李德俊； 董闯；

【作者基本信息】 大连理工大学 ， 材料学， 2003， 硕士

【摘要】 块状非晶态金属合金是90年代发展起来的一种新型亚稳态材料，它突破了传统甩带非晶的尺寸限制，可以作为工程结构材料使用，因此引起了人们对其力学性能研究的极大兴趣。本文选取具有很强非晶形成能力和晶化热稳定性的Zr基块状非晶态金属合金作为研究对象，采用负压铜模吸铸法制备成非晶棒样品。采用X射线衍射仪进行物相鉴定后，对其分别进行单轴压缩和动力学特性研究实验。室温单轴压缩实验利用Instron Universal-Testing Machine（IUTM）和扫描电子显微术（SEM）研究了Zr₆₅Al_7.5Ni₁₀Cu_17.5块状非晶的室温单轴压缩变形和断裂行为。结果表明：该合金的室温压缩变形过程表现为弹性和塑性变形，弹性应变很大，可达到2％。并且宏观形貌观察发现样品表面形成与压缩方向呈约45⁰的变形带。塑性变形主要集中在这一局部区域。塑性变形是以切变带粘性流层相对滑动的方式进行。在塑性变形阶段没有明显的加工硬化现象。塑性变形初期没有形成裂纹，当塑性变形积累到一定程度之后，裂纹在切变变形较大的区域表面形成。裂纹从萌生、扩展到断裂的时间极短。最终的断裂是流变积累和应力综合作用的结果。动力学特性实验是利用动态热分析仪（DMA）研究具有相同电子浓度、不同Zr、Al、Ni含量的三种非晶合金的贮存模量（G’），损耗模量（G”）和内耗（G”/G’）的动力学特性。结果表明，虽然三种非晶合金的电子浓度相同，但其动力学特性并不一样。在室温下，Zr含量最多的Zr₆₃Ni_18.5Al_18.5非晶合金具有最高的G’；在加热速度为10℃/min、振动频率为5Hz的条件下，三种非晶均在300℃左右开始发生G”和内耗，G”和内耗峰对应的温度随Zr含量的减少向高温方向推移，并且峰值降低。结合X射线结构分析得出G’开始下降的温度为晶化温度，它低于G”和内耗峰对应的温度。G”和内耗峰并不是出现在晶化的开始，而是出现在晶化过程中。而三种块状非晶态金属合金弹性模量和内耗的不同，可能与其结构短程序有关。更多还原

【Abstract】 Bulk metallic glasses are a family of unique metastable materials and the earliest reports date back to the studies of Zr-based multi-component systems in the 1990’s. The size limit in the formation of an amorphous solid thereafter has been broken through, and this opened a window for their applications as structural engineering materials. This, subsequently, has activated the research on their mechanical properties. Note that the Zr-based bulk metallic glasses manifest large forming abilities and thermal stabilities, in this thesis, we performed the studies on their mechanical properties. Zr65Al7.5Ni10Cu17.5 bulk metallic glass with 3mm in diameter were prepared by means of suction-casting method. The deformation and fracture behaviors under monaxial compression have been carried out on an Instron Univeral-Testing Machine at room temperature. We found: the samples experience elastic and plastic deformation processes before fracture, and the elastic strain is very large, it is about 2%. Shear bands along 45? angle with respect to the loading direction are observed in the cylinder of the deformed samples. The plastic deformation manifests a viscous flow behavior, and no work hardening is found during the plastic deformation process. Cracks form in the region where shear deformation is larger. As the plastic deformation accumulates in the origins of the cracks, fracture comes up and occurs in a very short time. The final fracture is mainly ascribed to the accumulation of the flow and the stress. To study the structure-property interrelation, the dynamical characteristics of storage modulus (G1), loss modulus (G1) and internal friction (G’/ G’) of three Zr-Al-Ni bulk metallic glasses were examined by the method of DMA. These samples are electronic concentration (e/a)-constant phases and their show different dynamical mechanical behaviors at room temperature. Zr63Ni18 5Al18 5 alloy has the largest value of G’ At the heat rate of 10C/min and the frequency of 5Hz, atomic relaxation occurs at about 300C in all the three samples. The peak temperature of G" and G"/ G’ tends to elevated temperature with Zr concentration, while the intensity of the peaks showing a decreasing tendency. Combining the results with the XRD analysis, we pointed out that the onset temperature of crystallization locates at the starting point of the G’ curve. The peak temperatures of G" and G"/ G’ cannot be regarded as the onset temperature of crystallization. In addition, the variation tendency of G" and G"/ G’ with respect to temperature, will provide information on the difference in local atomic structure of these e/a-constant bulk metallic glasses.更多还原