Characteristics of S/L Interface Evolution during High Rate Directional Solidification

The present paper aims to the characterization of high rate direction solidification on Al-Mn and Al-Cu alloys. It is indicated that the relevant cooling rate of high rate directional solidification is defined within 100～103 K/s that is located in the region between near-equilibrium slow growth rate and rapid solidification rate beyond equilibrium condition, and at the meantime there occurred a series of turning effect of interface stability and morphologies.With the increase of growth velocity the interface with planar front evolved to cells and dendrites at the stage of near-equilibrium and with further increase of growth rate they transformed reversely from dendrites to cell structure and then to absolute stability of planar interface. An explanation based on effective constitutional supercooling about the evolution of interface morphologies with the change of growth rate was proposed.