<i>In Situ</i> and Real-Time Observation of the Solidification Process of Al&ndash;20 mass%Cu Alloy by Synchrotron X-ray Radiography

Abstract

High brilliance synchrotron X-ray radiography has been used to in situ study the solidification process of Al20 mass%Cu alloy with nominal spatial and temporal resolutions of 7.4 µm and 300 ms, respectively. The block of favorably oriented dendrites by the unfavorably oriented ones was first observed in metal solidification, which related to solute interaction of neighbor dendrites. Solute interaction can also retard the growth of dendrites at the grain boundary, which makes the unusual overgrowth phenomenon possible. Fragmentation occurred when dendrite branches were detached from mother dendrite by local re-melting during the dendrite ripening. Fragmentations together with nucleated dendrites contributed to the columnar to equiaxed transition (CET) and the gravity played a significant role in the final microstructure due to the density difference between primary aluminum dendrites and the melt. In addition, the microporosity formation was observed in the inter-dendrite at the last stage of solidification.

Synchrotron quantification of ultrasound cavitation and bubble dynamics in Al–10Cu melts

“…In recent years, synchrotron X-ray imaging has been extensively applied to the in situ study of solidification [2,11,12], fragmentation [8,13] and coarsening mechanisms [14], pore and bubble growth during solidification [15,16], and semi-solid processing [17][18][19]. Huang et al [20] recently reported measurement of the size distribution of cavitation gas bubbles in an AlCu alloy melt using the synchrotron X-ray radiography whilst the current authors used it to study the ultrasonic capillary effect in a molten metallic alloy [21].…”

Scale up design study on process vessel dimensions for ultrasonic processing of water and liquid aluminium

“…A powerful tool in analysing and optimising the cavitation dynamics via synchrotron observation [19] , [20] , [21] (where only small-scale experiments are feasible and observations restricted in small volumes) is by measuring acoustic pressure emissions within the sonicated volume. Only handful of studies has been conducted so far on the characterization of cavitation-induced acoustic emissions in molten metals using high-temperature advanced sensors [2] , [3] , [14] , [22] , [23] , [24] , [25] , [26] , [27] .…”