CONTAINERLESS RAPID SOLIDIFICATION OF LIQUID Ti-Al-V ALLOYS INSIDE DROP TUBE

摘要

A short drop tube with 3m length and 10~(-3)g gravity was applied to realize the containerless rapid solidification of liquid Ti-6Al-4V, Ti-18Al-12V and Ti-30Al-20V alloys. The diameters of alloy droplets ranged from 65 to 1510μm, which corresponded to the cooling rates of 10~3～10~5 K/s and the undercooling levels of 200～700K. Bulk TC4 alloy melt was also undercooled by electromagnetic levitation technique and achieved a maximum undercooling of 208K (0.11T_L). The primary β phase usually grew in dendritic mode and then decomposed into basket weave microstructures, but sometimes was retained to ambient temperature at sufficiently high cooling rate. The microstructural evolution mechanisms were explored theoretically with the aids of SEM analyses.