The formation of macroscopic grain defects during the directional solidification of single crystal Ni-base superalloys can have a significant impact on resulting fatigue and creep properties of critical structural components used in a variety of aerospace applications and gas turbines for power generation. Common casting defects in Ni-base superalloys include freckles, Figure 1, which consist o...

Manufactured single crystal components using Ni-base super alloys are routinely used in the hot sections of aero engines and industrial gas turbines due to their outstanding high temperature strength, toughness and resistance to degradation in corrosive and oxidative environments. To control the quality of the single crystal turbine blades, particular attention has been paid to grain selection,...

2014 We investigate the stability of the planar front during directional solidification of a quasi-azeotrope. We show that the corresponding shape of the phase diagram induces a strong reduction of the scale of the bifurcation curve which makes its complete exploration feasible in standard directional solidification experiments. We show that the finite concentration of azeotropic mixtures resul...

Effect of a weak transverse magnetic field on the microstructures in directionally solidified Fe-Ni and Pb-Bi peritectic alloys has been investigated experimentally. The results indicate that the magnetic field can induce the formation of banded and island-like structures and refine the primary phase in peritectic alloys. The above results are enhanced with increasing magnetic field. Furthermor...

With a few exceptions, phase-field simulations of dendritic growth in cubic materials have been modeled using simple expressions for the interfacial energy anisotropy and with strong anisotropy. However, recent experimental results show that the Dendrite Orientation Transition (DOT) observed in Al-Zn alloys by Gonzales and Rappaz [Met. Mat. Trans. A37 (2006) 2797] occurs at weak anisotropy, and...

Pattern formation at the solid-liquid interface of a growing crystal was studied in directional solidification using a perturbation technique. We analyzed both experimentally and numerically the stability range and dynamical selection of cellular arrays of ‘‘doublets’’ with asymmetric tip shapes, separated by alternate deep and shallow grooves. Applying an initial periodic perturbation of arbit...

We present an experimental study of the surface effects (interactions with the container walls) during the nucleation and growth of smectic-B (SmB) crystals from the nematic in free growth and directional solidification of a mesogenic molecule [C4H9-(C6H10)2CN] called CCH4 in thin (of thickness in the 10-microm range) samples. We follow the dynamics of the system in real time with a polarizing ...

Ideas based on constitutional supercooling suggest that the periodic steady state cellular patterns seen in the directional solidification of systems with small partition coefficient may be unstable if the impurity concentration in the melt just in front of the tips falls into the two phase (miscibility gap) region of the phase diagram. This gives a simple stability criterion relating the posit...

We study the stability of a planar solid-melt boundary during directional solidification of a binary alloy when the solid is being periodically vibrated in the direction parallel to the boundary (or equivalently, under a far field uniform and oscillatory flow parallel to the planar boundary). The analysis is motivated by directional solidification experiments under the low level residual accele...