Homogeneous microstructure of bulk K4169 superalloy obtained by stable undercooling

By improving the method of B₂O₃ glass purification combined with cycle superheating based on traditional undercooling method, a stable undercooling above 200 K of 100 g bulk K4169 superalloy was obtained, and the largest undercooling went to 271 K. The effects of purification and superheating temperature on undercooling have been discussed. Moreover, the three-dimensional numerical analysis of temperature field inside the undercooled melt has been presented, and the maximum temperature deviation in different parts is only 14 K before nucleation. In contrast with the as-solidified microstructure, the grain size will increase with the increment of nucleating temperature. Generally, the difference of microstructure in 100 g undercooled K4169 superalloy is tiny and the average grain size of the superalloy with 271 K undercooling is 12±2 μm.