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Degassing LM25 aluminium alloy by novel degassing technology with intensive melt shearing

Abstract Hydrogen is the only gas that is appreciably soluble in aluminium and its alloys and is the main cause of the gas porosity in aluminium alloy castings. A novel degassing technology with intensive melt shearing and Ar injection has been developed and its degassing effect on aluminium alloy has been studied. The experimental results showed that the new degassing technology can significantly degas LM25 aluminium alloy within a quite short period of time. By applying intensive melt shearing and Ar injection of 60 s, the density index Di was reduced from 10·70 to 0·98%, which means that the hydrogen concentration in the liquid alloy was significantly reduced. The effect of degassing time and isothermal holding time after degassing on the hydrogen concentration level in LM25 alloy melt was also studied and the mechanism of high degassing efficiency with this technology was discussed.