Montanari Roberto, Varone Alessandra, Gregoratti Luca, Kaciulis Saulius, Mezzi Alessio
Department of Industrial Engineering, University of Rome "Tor Vergata", 00133 Roma, Italy.
Elettra - Sincrotrone di Trieste, Area Science Park, 34149 Trieste, Italy.
Materials (Basel). 2019 Sep 27;12(19):3158. doi: 10.3390/ma12193158.
Element clustering and structural features of liquid lead-bismuth eutectic (LBE) alloy have been investigated up to 720 °C by means of high temperature X-ray diffraction (HT-XRD), X-ray Photoemission Spectroscopy (XPS) and Scanning Photoemission Microscopy (SPEM) at the Elettra synchrotron in Trieste. The short-range order in liquid metal after melting corresponds to the cuboctahedral atomic arrangement and progressively evolves towards the icosahedral one as temperature increases. Such process, that involve a negative expansion of the alloy, is mainly connected to the reduction of atom distance in Pb-Pb pairs which takes place from 350 °C to 520 °C. On an atomic scale, it is observed a change of the relative number of Bi-Bi, Pb-Pb, and Pb-Bi pairs. The Pb-Bi pairs are detected only at a temperature above ~350 °C, and its fraction progressively increases, giving rise to a more homogeneous distribution of the elements. SPEM results showed evidence that the process of chemical homogenization on an atomic scale is preceded and accompanied by homogenization on micro-scale. Clusters rich of Bi and Pb, which are observed after melting, progressively dissolve as temperature increases: Only a few residuals remain at 350 °C, and no more clusters are detected a 520 °C.
通过在的里雅斯特的埃莱特拉同步加速器上进行高温X射线衍射（HT-XRD）、X射线光电子能谱（XPS）和扫描光电子显微镜（SPEM），对液态铅铋共晶（LBE）合金在高达720°C的温度下的元素聚类和结构特征进行了研究。液态金属熔化后的短程有序对应于立方八面体原子排列，并随着温度升高逐渐向二十面体排列演变。这种涉及合金负膨胀的过程，主要与350°C至520°C之间发生的Pb-Pb对中原子间距的减小有关。在原子尺度上，观察到Bi-Bi、Pb-Pb和Pb-Bi对的相对数量发生了变化。仅在约350°C以上的温度下检测到Pb-Bi对，并且其比例逐渐增加，导致元素分布更加均匀。SPEM结果表明，在原子尺度上的化学均匀化过程之前和伴随着微观尺度上的均匀化。熔化后观察到的富含Bi和Pb的团簇随着温度升高逐渐溶解：在350°C时仅残留少数团簇，在520°C时未检测到更多团簇。
