Temperature distribution in bottomless electromagnetic cold crucible applied to directional solidification

• A temperature measuring system was applied in cold crucible induction heating.
• A finite element model was established to calculate the temperature field in CCDS.
• The heat transfer of materials in cold crucible induction heating were studied.
• TiAl alloy was directionally solidified employing an optimized square cold crucible.

The novel technique of cold crucible directional solidification (CCDS) has been applied to prepare reactive and refractory metals and alloys with low or even no contamination. Microstructure formation is significantly influenced by heat transfer and temperature distribution in CCDS. The heating process and temperature distribution in two square cold crucibles designed for directional solidification were studied in this paper. A temperature-measuring device with anti-electromagnetic interference was devised to measure the temperature of Ti–46Al–6Nb (at.%), steel and aluminium (Al) ingots. A finite element (FE) model validated by experiment was used to calculate the temperature field in different materials. The results showed that the heating efficiency of cold crucible can be obviously improved by optimizing configuration. The temperature rise in heating process of all materials presents a slow tendency due to the heat loss. Compared with steel and Al, Ti–46Al–6Nb alloy exhibits the highest steady temperature even when the lowest power is applied, which is mainly attributed to the low heat conductivity. A Ti–46Al–6Nb ingot with the section of 30 mm × 30 mm was successfully directionally solidified under the power of 45 kW.