Growth and interaction of dendritic equiaxed grains: In situ characterization by synchrotron X-ray radiography

Quantitative Phase-field Simulation of Dendritic Equiaxed Growth and Comparison with in Situ Observation on Al – 4 wt.% Cu Alloy by Means of Synchrotron X-ray Radiography

“…After 440 seconds, the length of the isolated dendrite (Tip1) continues to increase while the other one (Tip2) is undergoing interaction so that its length reaches a plateau as a result of increasing solute poisoning by the opposite grain, which hinders its growth. These phase-field simulations are in agreement with the analysis performed by Bogno et al 13) in the case of dendritic equiaxed growth of Al -10 wt.% Cu alloys.…”

“…Detailed description of the solidification experiments can be found elsewhere. 13) A sequence of four recorded radiographs is shown in Fig. 1.…”

“…13) As the interface width and the dissipation time of the interface in the phase-field model, as well as the referred time and spatial units in simulations, are depending on the capillary length, such complexity of d0, which would make the model very intricate and hardly be feasible in practical simulations, will nevertheless be neglected. As dendrite growth from the melt occurs in time-dependent conditions during continuous cooling down, 13) the solute concentration in liquid at the dendrite tip is not constant but much lower than the equilibrium concentration c0/k at the solidus temperature, rather close to the initial concentration. Therefore, the capillary length is assumed constant at the nominal concentration of the alloy.…”

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.…”