The author found that during die-casting processes the primarily crystallised iron containing compounds in the Al-alloy had been filtered by the narrow gates of the dies having 0.7∼1 mm thickness.
Chemical analyses show that in the melts the iron content is 3.2%,in front of the gate 3.1% and in the die-casted materials 1.2%. The iron content is much lower in the die-casted materials than in the gate.
Microscophical observations show that the number of the iron containing compounds observed in the field (× 300) is 47 in front of the gate,but the number is 23 in the die-casted materials. The total surface area is 0.01417 mm2 in the former,but it is 0.00508 mm2 in the latter. It obviously show that the narrow gates of the dies have their filtering effects on the flow of the iron containing compounds in the Al alloys melts during die-casting process.
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