In situ observation of columnar-to-equiaxed transition in directional solidification using synchrotron X-radiation imaging technique

In situ study on growth behavior of Cu6Sn5 during solidification with an applied DC in RE-doped Sn–Cu solder alloys

“…Furthermore, the tipsplit manner [18], the refinement of ECP [20] and the stability of solidification interface morphology [21] were well explained by those mechanisms. In the last decade, many experiments have been conducted to real time and dynamically observe certain phenomena during solidification of liquid metals using synchrotron X-ray radiography with intense energy density, high brightness and monochromatic X-ray [18,[22][23][24].…”

In situ study the effect of refiner on the microstructure evolution of variable cross-section structure by synchrotron X-ray radiography

“…2a), which simulates the microstructure evolution that is observed at the variable cross-section region when casting using sequential solidification. There are two common mechanisms behind the columnar-to-equiaxed transition (CET): (1) the origin of the nuclei is located ahead of the columnar front [19,20] and (2) the dendrite fragments float to a position ahead of the columnar front resulting in the growth of equiaxed dendrites [21]. When the columnar dendrites from the thin-walled structure advanced into the large cross-section region, three secondary arms were observed to detach and float upwards into the melt due to differences in density caused by differences in the concentration of solute [21] (Fig.…”

“…In turn, this convection led to solute and temperature redistributed. Meanwhile, the secondary dendrite arms of the dendrite tip, which were prone to fracture due to the remelting of enriched solute and the shear force of convection, resulted in the formation of the observed dendritic fragments [21].…”

X‐ray Imaging and Controlled Solidification of Al‐Cu Alloys Toward Microstructures by Design

“…thermal conductivity, heat capacity, chemical potentials, etc.). Since early developments of synchrotron x-ray radiography for observing metal and alloy solidification, [10,[21][22][23] Al-based alloys have been extensively used to study numerous solidification aspects, from dendritic fragmentation, [6][7][8][9] columnar-to-equiaxed transition, [8,37,38] temperature gradient zone melting, [39] melt convection, [40] gravity, [41] polycrystalline solutal interactions, [42] and dendritic coarsening, [43] to semi-solid deformation [44][45][46][47][48] and permeability, [49] just to name a few. More recently, "microfocus" x-ray sources [50] have provided additional tools for real-time metal and alloy observations, enabling in situ imaging with laboratory-sized equipment previously only possible at large synchrotron facilities.…”

“…While our experiments did not provide sufficient statistical data regarding the frequency of such events, they are a longidentified problem. [1,10,11] In addition to strengthening our understanding of fundamental mechanisms at the origin of solidification defects, [6][7][8][9][10][19][20][21][22][23][37][38][39][40][41][42][43][44][45][46][47][48][49] in situ x-ray imaging with real-time monitoring and feedback control could be used to adapt processing routes to mitigate defects as they form and are detected. For instance, one could "erase" a microstructure by remelting it, and then control the subsequent microstructural development by refinement and live management of the processing parameters during solidification.…”