Rapid growth kinetics of intermetallic Ni₃Ti compound under electrostatic levitation state

The rapid solidification mechanism of Ni₃Ti intermetallic compound within undercooled Ni₇₅Ti₂₅ and Ni₇₄Ti₁₈Al₈ alloys was investigated by electrostatic levitation(ESL) and liquid quenching(LQ) techniques. The dendritic growth velocity of Ni₃Ti phase in these two alloys revealed power law relations versus liquid undercooling, whose maximum value was 138.9 mm s⁻¹ for binary Ni₇₅Ti₂₅ alloy at 255 K(0.15T_L) undercooling, while it was only 54.7 mm s⁻¹ at 222 K(0.13T_L) undercooling for ternary Ni₇₄Ti₁₈Al₈ alloy. The crystalline structure of Ni₃Ti phase in both alloys was characterized by fine dendrites under LQ state, whereas it displayed faceted growth mode under ESL condition. In addition, the Ni₃Ti grains of Ni₇₅Ti₂₅ alloy show a transition from incompletely to completely surrounded by the grain boundaries.