Influence of Trace Amounts of Phosphorus in Al Casting Alloys--A Review of the Literature

摘要

Impurity effects of phosphorus in Al-Si casting alloys, especially in hypoeutectic and eutectic alloys, were reviewed. While phosphorus serves as an effective primary silicon refiner in hypereutectic alloys, it is considered to be a harmful impurity in most hypoeutectic and eutectic alloys. Formation of the intermetallic compound, AlP, has been considered to be the main reason for the negative influence on both metallurgical and mechanical properties of Al-Si casting alloys. Also, interactions between phosphorus and the eutectic modifiers, such as sodium, strontium and antimony, have been clearly demonstrated. Chemical neutralization of phosphorus with sodium, strontium and antimony is perhaps the only way to nullify the detrimental effects of phosphorus in Al-Si casting alloys. Possibly, the tolerable amount of phosphorus contamination is less than 0.0005 percent (5 ppm) in hypoeutectic alloys and 0.001 percent (10 ppm) in eutectic alloys.