Formation Process And Control Method Of AlP In Phosphorus-Containing Master Alloys

The AlP formation in the intermediate alloy modifiers and the modification process is not clear,which leads to a problem in the control of the AlP particle size.In this paper,phosphorus-containing master alloy wad prepared in two ways,one by adding Cu-P alloy to pure aluminum,and the other by adding Cu-P alloy to the high Si-Al alloy melt.The AlP formation processes of pure Al mixed with Cu-9%P alloy,solid Cu-P alloy in contact with pure aluminum melt,and Cu-P alloy added into high Si-Al alloy melt are studied.At the same time,the influence of the mixing process of pure aluminum melt and the Si/Al ratio in the high Si-Al alloy on the AlP particle size in the phosphorus-containing master alloy are studied.The modification of Al-20%Si alloy is carried out with self-made phosphorus-containing master alloy and the modification effect is tested.The formation process of AlP in two kinds of master alloys has been revealed.That is,after the pure aluminum and Cu-9%P alloy melt contact,AlP is first formed on the interface;When Al diffuses into Cu-P alloy melt,it forms a solid Cu-Al-P alloy layer with Cu and reacts with P to form AlP at the same time;P which has diffused into liquid Cu-Al-P alloy region reacts with Al to form AlP.When the solid Cu-P alloy and the pure aluminum melt come into touch.Cu-P alloy particles are dissolved and release the Cu₃P phase.Cu₃P phase disintegrates and releases Cu atoms and P atoms to mix with aluminum melt,so forms a molten Cu-Al-P alloy layer around the undissolved Cu-P alloy.After Cu-P alloy added into high Si-Al alloy melt at 1700?,the Si-Cu-Al-P alloy melt is formed,and the AlP is formed in the melt solidification process.It is found that when Al-Cu-P master alloy is prepared by using Cu-P alloy and pure aluminum,the stirring of melt forces the AlP to leave the P-rich region after the formation of AlP,achieving the goal of controlling the growth of the AlP.At the stirring temperature of800?,stirring speed 300rad/min,stirring time is 20min,the size of AlP particles can be controlled within 2⁵?m.When Cu-P alloy is added to high Si-Al alloy melt to prepare Si-Cu-Al-P master alloy,and the Si/Al ratio in melt is 24,the size of AlP particles can be controlled within 2²0?m.The results show that the primary silicon of Al-20%Si alloy is refined by 81.6%and85.3%respectively after the modification of self-made Al-Cu-P and Si-Cu-Al-P master alloy,especially after the modification of Si-Cu-Al-P master alloy,the typical eutectic silicon basically disappears.To measure the effect of master alloy modifiers,the size of primary silicon after modification and the size of AlP in master alloy have basically consistent effects.