Effect Of Rare Earth Elements On Microstructure And Properties Of Al-Mg₂Si Alloy

This topic studied the iMPact of rare earth elements on mechanical properties of Al-Mg₂Si as well as morphology and distribution of Mg₂Si by adding different types, different content, different mixed rare earth elements,and obtained the best rare earth element and the element content of which improving the mechanical properties of Al-Mg₂Si alloy.An appropriate amount of rare earth elements can significantly refine the grain of Mg₂Si , improve their shape and distribution, circle primary Mg₂Si to a certain extent, meanwhile, it could also inhibit the anisotropic growth of Mg₂Si phase in eutectic phase. The best element of which refining the grain are La and Sc ,followed by Pr and Gd ,and Y is the worst.The shape of Mg₂Si is the best with La addition better than Gd ,and the shape of Mg₂Si with Pr,Sc,Y addition is the worst .Metamorphic effect of Mg₂Si with La addition is the best ,followed by Sc,Y,Pr,Gd.When rare earth element takes up 0.2% of the grossweight of the mixture ,most has been able to inhibit the dendrite growth of the primary crystal Mg₂Si to a certain extentt and make the primary Mg₂Si phase evenly distributed. For most rare earth elements,when they were added up to 0.6% 0.8 of the gross weight of the mixture,the phase of Mg₂Si showed the distribution of regular multilateral body, meanwhile, the microstructure has become smaller and the microstructure of primary crystal Mg₂Si was the best .When the RE content is further increased, the phase of the Mg₂Si turned irregular again, and Segregation growth of dendrite arise.At this time, RE-Al-Mg₂Si compounds is formed due to the aggregation of rare earth,and this dampened the impact on the Mg₂Si.The impact on the Mg₂Si was different with different mixed rare earth. The impact of mixed rare earth Ce & La was similar to La,the effect of mixed rare earthSc & La was similar to single Sc and La , the effect of mixed rare earth La & Y depended mainly on La and Y could weaken the effect of La to a certain extent . Electromagnetic stirring could make the distribution of Mg₂Si even and could refine the Mg₂Si primary phase,meanwhile , electromagnetic stirring could weaken the effect of La on primary Mg₂Si and eutectic Mg₂Si.The effect of rare earth elements on the mechanical properties of Al-30Mg₂Si alloys was discussed , the performance index-Tensile strength,elongation and hardness of the alloy showed a trendency which increase first and then decrease with the increase amount of rare earth.When using rare earth to deteriorate, in order to be better able to play the role of rare earth, better metamorphic Mg₂Si, must try to improve the cooling rate of cast. The greater the cooling rate, the more obvious modification effect.