The effect of fluid flow on the solidification of Ni2B from the undercooled melt

Abstract

In this work, we study the effect of fluid flow on the growth dynamics during solidification of tetragonal Ni 2 B from the undercooled melt. Different experimental techniques are applied to generate varying fluid flow velocities in undercooled samples, electromagnetic levitation under 1 g conditions (1 g EML) and in reduced gravity (lg EML) as well as the melt-fluxing technique and electrostatic levitation. The propagation of the solid-liquid interface apparent on the surface of solidifying samples is observed by high-speed video imaging while the non-contact measurement of the undercooling prior to solidification is accomplished by IR-pyrometry. It is demonstrated that fluid flow has a substantial influence on the growth kinetics. As revealed by an extended sharp-interface model, this effect is mainly attributed to the substantial change in growth kinetics caused by a convection induced transition from dendrites to more faceted solidification structures. V C 2014 AIP Publishing LLC. [http://dx.

Dendrite growth under forced convection: analysis methods and experimental tests

“…13 and details of calculations in paper [92]). The applicability of the theory is confirmed by its agreement with experiment under terrestrial and reduced gravity conditions in EML and ESL facilities and with the use of the melt fluxing technique [93]. Further development of research and independent verification of the adequacy of the above models for the available experimental data on the changes of growing crystal morphology should be focused on numerical simulations of solidification, taking account of the anisotropic properties of moving liquid±crystal interfaces and convective flows.…”

“…[92]), were utilized to calculate the dendritic growth rate as a function of supercooling. In addition to this set of equations, the peculiarities of the kinetic phase diagram were taken into account, determined by the liquidus slope and segregation coefficient in the functions of Ni 2 B crystal growth rate [92,93]. The results of calculations are shown in Fig.…”

Dendritic growth velocities in an undercooled melt of pure nickel under static magnetic fields: A test of theory with convection

“…A preliminary test of the AG theory has already been conducted using a two-dimensional formalism [20]. It was shown that the AG theory can provide a satisfactory explanation of the dendritic growth velocities observed in containerlessly undercooled intermetallic compounds in the presence of a convective flow in a bulk volume [20,21]. However, phase field modeling suggested that the influence of melt convection on a three-dimensional tip is more pronounced than on a two-dimensional tip [17,22].…”

Containerless Undercooled Melts: Ordering, Nucleation, and Dendrite Growth

“…These are EML on Earth (forced convection), EML in reduced gravity (reduced forced convection), melt fluxing technique (natural convection), melt fluxing in a strong external magnetic field (reduced natural convection), and electrostatic levitation on small samples (almost no convection). [87] 7. Intermetallic compound Ni 2 B: different levels of convection…”