| dc.description.abstract | This study used 1040 and 1020 carbon steels to simulate the materials of molds, and the aluminum melt adopted pure aluminum, Al-Mg alloy, Al-Si alloy and A356 separately. The growing of the Fe-Al compound was influenced respectively by the surface roughness formed oxide film, the carbon content of the carbon steel and sprayed talcum powder on the surface of the carbon steel and then investigated the influence of the magnesium and silicon contained in the aluminum melt.
Experimental results show:
1. It would form the barrier layer that was caused by the surface roughness of the carbon steel. With time increased, because the difference of the thermal expansion factor among aluminum oxide film and aluminum melt led to the crack of the aluminum oxide film, and the aluminum melt contacted the surface of the carbon steel directly.
2. Aluminum atoms diffused into ferrite along the ferrite grain boundary. During the growing of the Fe-Al compound, the carbon contained in the austenite that diffused, and stacked in the oxide or wrapped by the growing Fe-Al compound then formed the carbon channel.
3. The silicon contained in the aluminum melt reacted with the aluminum oxide film and dissolved it. In the initial stage, it made the carbon steel to contact the aluminum melt faster. But with the time increased, the silicon atoms diffused into between the carbon steel substrate and the Fe-Al compound then formed silicon carbide. It obstructed the growing of the Fe-Al compound and retarded the trend of growing time in long period.
4. The magnesium contained in the aluminum melt was apt to react with the aluminum oxide and formed spinel. It hindered between the Fe-Al compound and the aluminum melt.
5. Coating the talcum powder on the surface of the carbon steel can prevent the aluminum melt to contact the surface of the carbon steel effectively.
6. In the A356 alloy, it was apt to form the diverse oxide in the initial stage and decrease the probability of the thermal cracking. It made the thickness of the Fe-Al compound very thin in the initial stage. The aluminum melt and the silicon contained in the carbon steel retarded between the interface of the carbon steel substrate and the Fe-Al compound. | en_US |