The effect of various La levels on the reaction between pure iron panel and 55%Al-Zn-1?6 wt-%Si liquid baths during hot dipping at 600uC was investigated in this work. Three bath compositions containing 0, 0?2 and 0?5 wt-%La respectively, combined with six immersion times of 10, 60, 120, 180, 300 and 600 s, were studied. It was found that La can effectively control the formation of intermetallic layer by the synergistic effect with Si. The addition of La makes Si enriched in the intermetallic layer during the hot dipping. It hinders the formation of the Fe 2 Al 5 phase and promotes the growth of the t 5 phase. The intermetallic layer becomes more compact and uniform after the La was added. The intermetallic layer is composed of Fe 2 Al 5 (t 1 /t 9 ), FeAl 3 and t 5 phase. The diffusion path model was introduced to interpret the effect mechanism of La and Si in this work.

The influence of subrapid solidified processing parameters on the microstructure characteristic and grain refining efficiency of Al-5Ti-1B master alloy has been studied. The results show that the mean size of Al 3 Ti particles in Al-5Ti-1B master alloy decreases significantly after copper mould die casting. The morphology of Al 3 Ti particles changed from plate-like to blocky and petaloid. Compared with conventional Al-5Ti-1B master alloy, the phase constitution of subrapidly solidified Al-5Ti-1B master alloy does not change, and the improved master alloy shows a better grain refining efficiency. The microhardness of the pure aluminium refined by conventional and improved Al-5Tu-1B obeys the Hall-Petch relation, and the material constant k H is in the range of 84?02-91?80 MPa mm 1/2 . The mechanisms of grain refinement of aluminium by inoculation with improved Al-5Ti-1B master alloy are discussed based on the duplex nucleation theory and growth restriction effects in aluminium alloys.