Effect of micro alloying elements on the interfacial reactions between molten aluminum alloy and tool steel

摘要

The morphology and growth kinetics of intermetallic compounds that are formed in the interface of H13 tool steel and A380 molten aluminum has been investigated through immersion experiments. The effect of addition of micro alloying elements to the melt on the formation and thickness of intermetallic layer was also studied. Microstructural investigation showed that three intermetallic layers formed through the liquid-solid reaction during immersion of steel samples in the liquid aluminum at a temperature of 680 deg C for the duration time of 2min to 2.5 h. These intermetallic compounds are Al_8Fe_2Si, Al_5FeSi and Al_(12)Fe_5Si. The effect of nitride coating of the surface of H13 steel on the growth of intermetallic phases has also been studied. Micro alloying elements such as strontium and titanium have been used in the melt and their effects on the morphology of intermetallic compound and their growth rate have been investigated by the immersion experiments at the temperature of 680 deg C for the time of 0.5-2.5 h. The results showed that two layers of AlsFe_2Si and Al_5FeSi formed at the interface and Al_(12)Fe_5Si layer was not observed. Nitride coating decreased the overall thickness of the intermetallic layer about 50 percent after immersion time of 0.5 h. Addition of micro alloying elements such as Sr (0.05 wt percent ) and Ti (0.2 wt percent ) to the melt decreased the total thickness of the intermetallic layer about 31 percent after immersion of steel for 0.5 h in the melt. Both nitride coating and addition of strontium (0.05 wt percent ) and titanium (0.2 wt percent ) micro alloying elements to the melt had the most influence on decreasing the overall thickness of the intermetallic layer. The thickness of the intermetallic layer decreased about 60 percent after immersion of steel for 2.5 h in the aluminum melt. The experimental results clearly indicate the beneficial effect of strontium on the kinetics of the formation and growth of the intermetallic layers.