Effects Of Rare Earth Elements(La,Ce) Addition On Microstructures And Mechanical Properties Of AlSi10MgMn Alloy

As an important series of cast aluminum alloy,cast aluminum silicon alloy is widely used in automobile,aviation,aerospace and other industries due to its good mechanical properties,castability and corrosion resistance.The addition of La and Ce in the casting aluminum alloy can purify the alloy liquid,refine the grain and improve the structure,so as to significantly improve the casting performance and mechanical properties of the alloy.Therefore,it is of great significance to study the role of rare earth?La,Ce?in casting aluminum alloy for the development of new high performance aluminum alloy.In this experiment,four kinds of AlSi10MgMn alloy plates with different content of rare earth were prepared by gravity casting,using the AlSi10MgMn alloy designed by ourselves as the base alloy and adding different lanthanum cerium mixed rare earth.Optical microscope,scanning electron microscope,Vickers hardness and tensile test at room temperature were used,The effects of different rare earth additions on the as cast and solution microstructure and properties of alsi10mgmn alloy were studied,and the heat treatment process of 0.1wt%RE alloy was explored.The results show that:The mixed rare earth?La,Ce?can refine?-Al,eutectic silicon,Mg₂Si and AlMnSi phases in alsi10mgmn alloy to varying degrees.After adding rare earth,?-AlFeSi phase disappeared,?-Al and eutectic silicon size decreased;The Mg₂Si phase in the form of thick petals was transformed into fine and dispersed granules;AlMnSi phase block decreased,and with the increase of rare earth content,there was a trend from coarse block to Y-shaped bone to fishbone to strip.The addition of rare earth?La,Ce?also resulted in the formation of Al₁₁La₃ and Al₁₁Ce₃ rare earth phases with strengthening effect.Adding a small amount of rare earth?La,Ce?can improve the hardness and tensile strength of the alloy,but reduce the elongation of the alloy.If the content of rare earth is too high,it will reduce the hardness and strength of the alloy,and increase the elongation.When 0.1wt%RE is added to as cast alsi10mgmn alloy,the microstructure and comprehensive properties of the alloy are better.The hardness,tensile strength and yield strength of the alloy are 82.76HV,373.05MPa and 281.37MPa,respectively,which are12.95%,17.29%and 43.44%higher than those of the alloy without rare earth,and the elongation is 2.26%,11.37%lower than that of the alloy without rare earth;Under the condition of 530?,6.5h solution treatment,0.1wt%RE alloy has batter microstructure and comprehensive properties,the eutectic silicon particles are smaller in the microstructure,the hardness,tensile strength and elongation are 109.92HV,424.84MPa and 2.72%respectively,which are 32.82%,13.88%and 20.35%higher than those of the as cast alloy;The best heat treatment process of adding 0.1wt%RE alloy is 530?,6.5h solid solution,170?,9h aging.At this time,there are a large number of??phases in the alloy,and a small amount of fine and dispersed rare earth phases are also precipitated,The hardness and tensile strength of the alloy are 160.99HV and 563.41MPa respectively,which are94.53%and 51.03%higher than that of the as cast alloy.the elongation is 2.25% and 0.44% lower.There are a lot of AlMnSi,eutectic silicon and a small amount of Mg₂Si phase at the fracture of cast AlSi10MgMn alloy,which are brittle cleavage and intergranular mixed fracture.The addition of rare earth?La,Ce?,solution treatment and aging treatment have no effect on the fracture mode of the alloy.