小角X射线散射表征非晶合金纳米尺度结构非均匀  

Characterization of nanoscale structural heterogeneity in an amorphous alloy by synchrotron small angle X-ray scattering

作　　者：孙星 默广[3] 赵林志 戴兰宏[1,2] 吴忠华 蒋敏强[1,2] 

机构地区：[1]中国科学院力学研究所,非线性力学国家重点实验室,北京100190 [2]中国科学院大学工程科学学院,北京100049 [3]中国科学院高能物理研究所,同步辐射实验室,北京100039 [4]中国科学院物理研究所,北京100190

出　　处：《物理学报》2017年第17期99-108,共10页Acta Physica Sinica

基　　金：国家优秀青年科学基金(批准号:11522221);国家自然科学基金(批准号:11372315,11472287);中国科学院前沿科学重点研究项目(批准号:QYZDJSSW-JSC011);中国科学院战略性科技先导专项(B类)(批准号:XDB22040303)资助的课题~~

摘　　要：表征纳米尺度结构非均匀对于理解非晶合金的变形、弛豫等动力学行为至关重要.受时空尺度限制,非晶合金纳米尺度结构非均匀的实验表征具有很大的挑战性.本文针对一种典型的锆基非晶合金,开展了同步辐射小角X射线散射原位拉伸实验.通过对散射曲线的定量分析,揭示了非晶合金在纳米尺度的非均匀结构图像.首先,Porod散射曲线呈现正偏离行为,表明非晶合金属于非理想两相散射体系,两相界面弥散且任一相内都存在电子密度涨落.基于散射曲线的Guinier定律分析,进一步揭示非晶合金中散射体形状远偏离球形,其特征尺度主要分布在0.8—1.6 nm之间,且在弹性变形阶段几乎不变.最后,通过Debye相关函数分析,发现这些纳米尺度散射体仅在1 nm之内存在强关联,符合非晶合金短程有序、长程无序的结构特征.研究结果表明非晶合金中存在具有复杂空间分布的纳米尺度非均匀结构.Amorphous alloys are the glassy solids that are formed through the glass transition of high-temperature melts. They therefore inherit the long-ranger disorders of melts and many quenched-in defects such as free volume. This inevitably leads to structural heterogeneity on a nanoscale that is believed to be as fertile sites for initiating relaxation and flow However, due to limitations of spatiotemporal measurements, experimental characterization of the nanoscale structural heterogeneity in amorphous alloys has faced a great challenges. In this paper, an in-situ tensile testing setup with synchrotron small angle X-ray scattering is designed for a Zr-based （Vitreloy i） amorphous alloy. By the small angle X-ray scattering, the structural heterogeneity of the Vitreloy 1 amorphous alloy can be described by the fluctuation of electron density. The small angle scattering images are recorded with the charge coupled device （CCD） detector and then are azimuthally integrated into the one-dimensional scattering intensity curves using the FIT2D software. We apply the Porod law, Guinier law and Debye law to the obtained scattering intensity curves, and attempt to obtain the information about structural heterogeneity in the Vitreloy 1 amorphous alloy at different stress levels The results indicate that the scattering intensity curve of the Vitreloy 1 amorphous alloy exhibits the positive deviation of Porod law. This observation proves that the amorphous alloy belongs to the non-ideal two-phase system corresponding to the complicated spatial distribution between soft/liquid-like and hard/solid-like phases. According to the Porod＇s law, it is revealed that the diffuse interface exists between the two phases, associated with the density fluctuations in either of phases. ~rthermore, we demonstrate that different scatterers coexist in the amorphous alloy and their characteristic sizes measured by the radius of gyration are mainly distributed between 0.8 nm and 1.6 am. It deserves to note that the range of radii of gyration

关 键 词：非晶合金 纳米尺度结构非均匀 小角X射线散射 变形 

分 类 号：O434.1[机械工程—光学工程] TG139.8[理学—光学]