Influence Of Melt Stirring Process On The Effect Of P Modification Of Hypereutectic Al-Si Alloy

Hypereutectic Al-Si alloy has the advantages of small thermal expansion coefficient,good thermal stability,low density,high hardness,high temperature resistance and good wear resistance.So it has a good application prospect in the fields of engine parts materials.Modification is often used to refine the primary Si in the hypereutectic Al-Si alloy.The effect of P modification on the refinement of the primary Si is obvious,stable and easy among many modification methods.The melt can obtain better modification effect by stirring after adding the master alloy containing P to the hypereutectic Al-Si alloy.However,the influence law of stirring extent on the modification effect is not clear.The influence law of melt stirring process on the modification effect is studied by using Cu-9 % P alloy to refine the primary Si in the Al-15 % Si,Al-18 % Si and Al-20 % Si.It provides a theoretical basis for the making full use of the P modifcation.The experimental results show that the average size of the primary Si decreased first and then increased with the extension of time and the more intense the stirring is,the better the refining effect is when the stirring temperature is more than melting temperature of Cu-9 % P for Al-20 % Si alloy.When the stirring speed is 224rad/min and the stirring time is 8min,the average size of the primary Si reaches 17?m.When the stirring temperature is less than melting temperature of Cu-9 % P alloy,the average size of the primary Si decreased first and then decreased generally with the extension of the stirring time for the Al-15 % Si,Al-18 % Si and Al-20 % Si alloy.The more intense the stirring is,the better the refining effect of the primary Si is in the best stirring time.When the stirring time is too long,the longer the stirring time is,the larger the size of the primary Si is.The best stirring time is 20 min that is not related to the Si content.The best stirring time is different when the Si content is different at the low stirring speed(224rad/min).The average size of the primary Si reaches 9?m for Al-15 % Si alloy and that reaches 17?m for Al-18 % Si alloy when the stirring speed is 224rad/min and the stirring time is 20 min.For Al-20 % Si alloy,the average size of the primary Si reaches 12?m,the typical eutectic structure disappeared and the granular eutectic Si appeared.The higher the Si content is,the more the average of the primary Si decreases,the more obvious the refining effect is.