The role of Ti and Si in the nucleation of α-Al during hot dip coating of steel with Al–43.4 wt.%Zn–1.6 wt.%Si alloy

• A nucleation model of 55 wt.%Al–Zn–1.6Si by Al–5Ti–0.2B master alloy
• Comparing the stability of TiAl3 and Ti(Al,Si)3 by first principle calculation
• Calculating the lattice mismatch between TiAl3 and Al matrix

The effect of Ti and Si on the nucleation of primary α-Al from the Al–43.4 wt.%Zn − 1.6 wt.%Si alloy was studied by adding Al–Ti–B to the master alloy during cooling and solidification. The effect of Si on the stability of the TiAl3/Al interface was analyzed by performing first principles calculations. The results showed that TiAl3 and the Al matrix possessed good lattice coherency, and other phases were not generated at the TiAl3/α-Al interface, according to the diffraction patterns. The interface bonding energy (vector) of TiAl3/Al decreased when Si was inserted at the Al position of the TiAl3 crystal structure, increasing the stability of the TiAl3/α-Al interface and enhancing nucleation.