The experiment of hot dip aluminizing had been carried out in order to study the interaction between die casting die and aluminum alloy and the effect of Si on soldering tendency between die and aluminum alloy casting. The experimental results show that Fe 2Al 5 phase layer and FeAl 3 phase are formed when samples of die steel are dipped in pure Al melt

and Fe 2Al 5 phase is the predominant phase of reaction diffusion. Two phase layers of FeSiAl 3 and Fe 2Al 5 are formed when samples are dipped in A380 melt. Because the existence of Si reduces the activity coefficient of Al in the phase layer of FeSiAl 3 and decreases the number of aluminum atoms

supplied from molten Al to Fe 2Al 5 phase

the fast growth of Fe 2Al 5 phase is restrained. Therefore

the element Si in aluminum alloy reduces the interaction between die steel and aluminum alloy melt and reduces the soldering tendency of aluminum die casting. The restraining effect of Si on the Fe 2l 3 phase layer growth decreases with temperature decreasing of hot dip aluminizing.