Evolution of dendritic patterns during alloy solidification: Onset of the initial instability

AUTOR(ES)

Losert, W.

FONTE

The National Academy of Sciences

RESUMO

The evolution of a dendritic pattern from a planar solid–liquid interface during directional solidification of a binary alloy was investigated experimentally. The model alloy used was the transparent organic crystal succinonitrile doped with the laser dye coumarin 152. The buildup of solute ahead of the initially stable planar interface and the subsequent instability of the planar front were measured in detail and compared with recent theoretical calculations by Warren and Langer [Warren, J. A. & Langer, J. S. (1993) Phys. Rev. E 47, 2702- 2712]. The fluorescence of coumarin 152 was used for direct observations of the evolution of the solute concentration profile ahead of the initially planar solid–liquid interface. UV absorption was used to produce thermal perturbations of the sample that generated spatially periodic modulations of the planar interface. This technique allows for measurement of both positive and negative linear growth coefficients (determined from the growth or decay rate of the modulation after the perturbation is switched off) for a large range of wave vectors. Measurements of the evolution of the concentration profile and the linear growth coefficients, and the occurrence of the initial instability, were in good agreement with the Warren–Langer predictions.

Documentos Relacionados

• Evolution of dendritic patterns during alloy solidification: From the initial instability to the steady state
• Predicting Secondary-Dendrite Arm Spacing of the Al-4.5wt%Cu Alloy During Unidirectional Solidification
• Microstructural evolution and mechanical properties of Sn-Bi-Cu ternary eutectic alloy produced by directional solidification
• Evolution of eutectic spacing during unidirectional solidification of Al-Ni alloys
• Macroscopic modeling of columnar dendritic solidification