脉冲电流对冷坩埚定向凝固 TiAl 基合金微观组织和性能的影响

Referring to the simulation results, the effects of pulse current with different parameters on the solidification structure and properties of directionally solidified Ti-45.5Al-4Cr-2.5Nb (%, atom fraction) alloy were investigated. The results show that when the pulse current frequency is 200 Hz, due to the skin effect of current and Joule heat effect of current the surface current of melt is biased and the lateral heat dissipation decreases, the average deviation angle of dendrite decreases, and the elongation increases with the decrease of deviation angle. When the density of pulse current is small, the average width of grains decreases with the increase of current density due to Joule heat effect of current and electromagnetic stirring which promote the remelting or breaking of dendrites. However, when the current density reaches a certain value, the melting zone grows up and the temperature gradient decreases. On the contrary, the average width of grains increases and the tensile strength of TiAl alloy first increases with the increase of current density, and then decreases; Compared with the master alloy ingot, the tensile strength and elongation of TiAl alloy increased by 70.7% and 129.5% respectively.