Interphase anisotropy effects on lamellar eutectics: a numerical study.

In directional solidification of binary eutectics, it is often observed that two-phase lamellar growth patterns grow tilted with respect to the direction z of the imposed temperature gradient. This crystallographic effect depends on the orientation of the two crystal phases α and β with respect to z. Recently, an approximate theory was formulated that predicts the lamellar tilt angle as a function of the anisotropy of the free energy of the solid(α)-solid(β) interphase boundary.

Scaling theory of two-phase dendritic growth in undercooled ternary melts.

Two-phase dendrites are needlelike crystals with a eutectic internal structure growing during solidification of ternary alloys. We present a scaling theory of these objects based on Ivantsov's theory of dendritic growth and the Jackson-Hunt theory of eutectic growth. The additional introduction of the relationship ρ∼λ (ρ: dendrite tip radius; λ: eutectic interphase spacing) suggested by recent experimental results [S.

Spiral two-phase dendrites.

We present real-time observations of a new growth pattern called a spiral two-phase dendrite, which we observed during univariant directional solidification of a ternary-eutectic alloy. Two different crystal phases grow from the apex of a parabolic finger, forming a spiral pattern that leaves behind in the solid a double helix microstructure. The parabola tip radius is nearly equal to the helix step.

Weakly faceted cellular patterns versus growth-induced plastic deformation in thin-sample directional solidification of monoclinic biphenyl.

We present an experimental study of thin-sample directional solidification (T-DS) in impure biphenyl. The platelike growth shape of the monoclinic biphenyl crystals includes two low-mobility (001) facets and four high-mobility {110} facets. Upon T-DS, biphenyl plates oriented with (001) facets parallel to the sample plane can exhibit either a strong growth-induced plastic deformation (GID), or deformation-free weakly faceted (WF) growth patterns.

Long-time dynamics of the directional solidification of rodlike eutectics.

We report long-duration real-time observations of the dynamics of hexagonal (rodlike) directional-solidification patterns in bulk samples of a transparent eutectic alloy. A slight forward curvature of the isotherms induces a slow dilatation of the growth pattern at constant solidification rate and triggers the rod-splitting instability. At long times, the rod-splitting frequency exactly balances the dilatation driven by the curved isotherms.

Experimental evidence for a zigzag bifurcation in bulk lamellar eutectic growth.

We present real-time observations of the directional-solidification patterns of a transparent nonfaceted eutectic alloy (CBr4-C2Cl6) in bulk samples. The growth front of the two-phase solid is observed from the top through the liquid and the glass wall of the container with a long-distance microscope. We show that, in near-eutectic CBr4-C2Cl6 alloys, the upper stability limit of the stationary lamellar patterns is due to a zigzag bifurcation, which occurs at an interlamellar spacing of about 0.