Rapid Crystal Growth Of Ag-Cu-Ge Ternary Eutectic Alloy

Rapid solidification of ternary eutectic alloys is an important research subject in the field of materials science. The rapid solidification of Ag-Cu-Ge ternary eutectic alloys was accomplished respectively by glass fluxing, drop tube and melt spinning method. The thesis has performed detailed investigations on phase constitution and characteristics of solidified microstructure under above conditions, which can reveal the mechanism of rapid solidification and crystal growth.By using glass fluxing equipment, the liquid Ag_38.5Cu_33.4Ge_28.1 ternary eutectic alloy was undercooled by a great degree up to 175 K(0.227_e). X-ray diffraction analysis reveals that its microstructure is composed of (Ag) solid solution phase, (Ge) semiconducting phase and η(Cu₃Ge) intermetallic compound phase in different undercoolings. With the increase of undercooling, there occurs a transition from the cooperative growth of three eutectic phases to the (Ge) phase separates from (Ag)+η two-phase eutectic. When the undercooling exceeds 80 K, the structural morphology of primary (Ge) phase transfers from faceted blocks into branched dendrites. Some (Ge) dendrites look like flowers. Both theoretical analysis and experimental results indicate that (Ge) phase is the primary phase.Rapid solidification of Ag_38.5Cu_33.4Ge_28.1 ternary eutectic alloy during containerless conditions is studied in experiment, and the maximum supercooling is up to 200 K(0.257_l). The results present that the rapid solidification microstructure consists of (Ge) primary phase, (Ag)+η two-phase irregular lamellar eutectic and (Ge)+(Ag)+η ternary irregular lamellar eutectic. When the undercooling exceeds 200 K, the primary phase and pseudobinary eutectic disappear, and microstructure refinement of ternary eutectic occurs. A kind of spherical anomalous ternary grains appears in deep undercooling conditions. The differences in morphology of (Ge) phase imply a transition from faceted growth to non-faceted growth with increasing undercooling.AG_38.5Cu_33.4Ge_28.1 eutectic alloy ribbon with a thick of 17.5 μm is obtained by melt spinning method. The rapid solidified microstructure is proved to be composed...