Rare earth is explained in rounding of aluminum and its alloys

Studies show that of Al - Si metamorphic process directly affects the bad effect of rare earths. Stability metamorphic organization is the key to reduce the loss of rare earth, and to prevent the rare earth together, in the rare earth evenly spread rapidly to the liquid Alumina Oxides; In order to obtain stable metamorphic organization, should as far as possible to improve metamorphic temperature, metamorphic strengthen let stand, after strictly grilled slag after refining, and as far as possible need not halogen element flux for refining and cover. Rare-earth has certain incubation period, must maintain a certain amount of time at high temperature, rare earth can maximize metamorphism.
Purification effect
Rare earths to gas and the impact on the rate of pinhole
Aluminum and its alloy in the casting process, a large amount of gas will dissolve in liquid aluminum, mainly hydrogen (about 85% of gas in liquid aluminum), followed by oxygen and nitrogen. Hydrogen source is mainly in charge of water vapor, aluminum ingots and leftover material of oil, water, and on the surface of the aluminium ingot aluminum "rust" - Al (OH) 3. Hydrogen is the main reason for the aluminum powders casting of pinhole, and significantly reduce the strength of the aluminum. All can in rare earth added to the aluminum and its alloy degassing effect. When less than 0.3% for the amount of rare earth, rare earth in addition to the obvious effect of hydrogen, reduce the amplitude of pinhole rate is the largest also. After more than 0.3% when the content of rare earth, rare earth content increases, the hydrogen content is slowed down. If Y, single rare earth La, when rare earth content more than 0.3%, the increase of the content of rare earth makes hydrogen content started to rise again, changes in the rate of pinhole has the same rule, but the change is more obvious. The author thinks that to hydrogen effect in order to Y > La > Re (mixed rare earth); From the content, a single rare earth content is less than 0.3%. Rare earth with oxygen, nitrogen can generate a kind of refractory compounds Re2O3 and ReN2. In the process of smelting, mostly in the form of slag elimination; At the same time, when temperature is less than 200 ℃, rare earth and fluorine, chlorine violent action can generate of rare earth and rare earth chloride, fluoride to remove fluorine and chlorine in aluminum. So, the rare earth in the aluminum alloy can be used as purifying agent.