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.