Dendritic and eutectic growth in Sb60Ag20Cu20 ternary alloy

Abstract

The rapid solidification of Sb 60 Ag 20 Cu 20 ternary alloy was realized by high undercooling method, and the maximum undercooling is up to 142 K (0.18T L ). Within the wide undercooling range of 40-142 K, the solidified microstructures are composed of (Sb), θ and ε phases. High undercooling enlarges the solute solubility of (Sb) phase, which causes its crystal lattice to expand and its crystal lattice constants to increase. Primary (Sb) phase grows in two modes: at small undercoolings non-faceted dendrite growth is the main growth form; whereas at large undercoolings faceted dendrite growth takes the dominant place. The remarkable difference of crystal structures between (Sb) and θ phases leads to (θ + Sb) pseudobinary eutectic hard to form, whereas strips of θ form when the alloy melt reaches the (θ + Sb) pseudobinary eutectic line. The cooperative growth of θ and ε phases contributes to the formation of (ε + θ ) pseudobinary eutectic easily. In addition, the crystallization route has been determined via microstructural characteristic analysis and DSC experiment.high undercooling, ternary eutectic, crystal nucleation, dendrite growth Rapid crystal growth at high undercooling is a liquid/solid phase transition process deviating far from the equilibrium situation, which has been investigated widely to develop metal solidification mechanism and prepare novel metal materials [1][2][3][4][5] . It has been achieved by means of various containerless techniques, such as glass fluxing technique, drop tube technique and various kinds of levitation techniques [6][7][8] . Recently more attention has been attracted on the rapid crystal growth of undercooled ternary alloy. Sb-Ag-Cu ternary eutectic alloy system has a low eutectic transition temperature (699 K), whose solidification process involves the competitive nucleation and growth of several solid solutions and intermetallic compounds including faceted and nonfaceted phases.Faceted and non-faceted growth are two types of crystal growth. Faceted growth is realized by liquid phase atoms depositing on the steps of S/L interface which is flat on an atomic scale.

Solidification microstructure and phase constitution of Fe-7.5%Mo-16.5%Si ternary quasiperitectic alloy

“…Ternary alloy systems involve very complicated phase transition and solidification process. Hence, a solidification theory on ternary alloys has not been established up to now [10][11][12]. Especially, little information is available on ternary quasiperitectic alloys.…”