Solidification microstructures and solid-state parallels: Recent developments, future directions

Abstract

Rapid advances in atomistic and phase-field modeling techniques as well as new experiments have led to major progress in solidification science during the first years of this century. Here we review the most important findings in this technologically important area that impact our quantitative understanding of: (i) key anisotropic properties of the solid-liquid interface that govern solidification pattern evolution, including the solid-liquid interface free energy and the kinetic coefficient; (ii) dendritic solidification at small and large growth rates, with particular emphasis on orientation selection; (iii) regular and irregular eutectic and peritectic microstructures; (iv) effects of convection on microstructure formation; (v) solidification at a high volume fraction of solid and the related formation of pores and hot cracks; and (vi) solid-state transformations as far as they relate to solidification models and techniques. In light of this progress, critical issues that point to directions for future research in both solidification and solid-state transformations are identified.

Dendritic Growth Morphologies in Al-Zn Alloys—Part II: Phase-Field Computations

“…We surveyed the anisotropy parameter space using a similar approach, i.e., using line scans. Since all of the available experimental and MD data [28] show that these parameters are in the range 0 £ a 1 £ 0.12 and À0.01 £ a 2 £ 0, the (a 1 , a 2 ) couples were chosen as indicated in Figure 2, which also provides a sampling of the computed microstructures. In particular, the diagonal scan line was chosen to go approximately through the following points: (a 1 , Àa 2 ) = (0.07, 0.0), measured by Napolitano et al [29] for Al-Si alloys; (a 1 , Àa 2 ) = (0.05, 0.0045) obtained by MD simulations using the embedded atom method [30] ; and (a 1 , Àa 2 ) = (À0.025 ± 0.023, 0.024 ± 0.014) measured recently by Friedli for quenched droplets in Al-82 wt pct Zn alloys.…”

X-Ray Videomicroscopy Studies of Eutectic Al-Si Solidification in Al-Si-Cu

“…[8] Nevertheless, for irregular eutectics, the branching stiffness of the faceted phase gives rise to the formation of a truly three-dimensional (3-D) eutectic microstructure, where a governing theory for assessment of pattern selection criteria and microstructure characteristics is still missing. [9] In hypoeutectic Al-Si alloys, the a-Al primary can be refined efficiently by means of TiB 2 inoculation. In addition, further improvements in cast component performance are available through modification of the eutectic microstructure, either by employing a high cooling rate or by relatively modest melt additions of certain elements such as Sr, Na, Sb, or Ca.…”

Orientation selection of equiaxed dendritic growth by three-dimensional cellular automaton model

“…The solidification microstructures, which generally determine the final properties of the relative product to a large extent [1,2] , have been focused by the physicists and material scientists for several decades. Dendrite is the most common microstructures observed in the casting products of commercial alloys [3][4][5][6][7][8] .…”