Microchemical inhomogeneity in eutectic Pb–Bi alloy quenched from melt

Abstract

The liquid lead-bismuth eutectic alloy is of great interest for applications in advanced nuclear systems; in particular, it is considered to be a good candidate as a coolant and neutron spallation source material for MYRRHA (http://myrrha.sckcen.be/), an accelerator driven system. Investigations based on mechanical spectroscopy experiments and high-temperature X-ray diffraction evidenced that the structure of the liquid alloy is not stable but undergoes relevant changes as the temperature increases. To understand whether such transformations, occurring in the liquid state involve elemental clustering, the alloy has been waterquenched from the liquid state at three different temperatures. After quenching, the samples have been investigated by standard XPS and scanning photoemission microscopy at the ELETTRA synchrotron. The SPEM results showed that the distribution of two metals is characterised by the following: (i) Pb-enriched clusters, (ii) Bi-enriched clusters and (iii) matrix in near eutectic composition. The statistics of clusters size was evaluated from the linescans of chemical Pb/Bi images. The average size of clusters is noticeably reduced by increasing quenching temperature: it is in the range of 1 ÷ 3 μm at 313°C and passes to 0.5 ÷ 0.9 μm at 518°C. Therefore, scanning photoemission microscopy results evidenced a structural and microchemical rearrangement of the atoms in the melt consisting in the evolution of cluster size and composition.

ESCA as a Tool for Exploration of Metals’ Surface

“…Therefore, it is quite important to investigate any changes of the microchemical structure of LBE that may induce corrosion and embrittlement phenomena in the structural materials. The microstructure of the LBE alloy was evaluated using high-temperature X-ray diffraction (HT-XRD) [33], whereas the microchemical composition was investigated by SPEM [34][35][36].…”

Physical Phenomena Leading to Melting of Metals

“…The alloys examined in the present work belong to the systems In-Sn and Pb-Bi and have been already investigated by us in the liquid state [42][43][44][45].…”

Temperature Dependent Phenomena in Liquid LBE Alloy

“…Possible clustering of alloying elements has been investigated by XPS and scanning photoemission microscopy (SPEM) at the ELETTRA synchrotron (Trieste, Italy). The SPEM technique was employed due to its high lateral resolution (below 50 nm) [13][14][15]. LBE has been kept for 1 hour at some selected temperatures to get a complete thermal stabilization, then has been water quenched with a cooling rate that substantially permits to get a chemical distribution close to that at high temperature.…”