Effect Of Rare Earth Micro Alloying On Microstructure And Properties Of Al-4Cu-1.5Mg-Mn Alloy

By improving the microstructure of aluminum alloy materials,to further improve its comprehensive properties,has been a hot topic in the field of research..This paper put the Al-4Cu-1.5Mg-Mn alloy which is the most typical in Al-Cu-Mg-Mn system as research objects.By adding two kinds of rare earth elements scandium（Sc）and lanthanum（La）to the alloy,heating,smelting,refining and casting in a general well type crucible resistance furnace.Observe the metallographic structure under the optical microscope and find out the effect of rare earth elements on the microstructure and mechanical properties of Al-Cu-Mg-Mn alloy.The best heat treatment of Al-Cu-Mg-Mn alloy contains rare earth.By means of mechanical property test,SEM and EDS,the optimal amount of rare earth in the alloy and the optimum heat treatment process were sought.The results are shown as follows:1.The microstructure and mechanical properties of cast dendrite of Al-4Cu-1.5Mg-Mn alloy can be improved effectively by adding trace rare earth elements Sc and La.With the increase of the content of rare earth elements,the mechanical properties of Al-4Cu-1.5Mg-Mn alloy first increased and then decreased.And when the content of Sc is0.4%,the content of La is 0.3%,the best condition is reached.2.Addition of SC alloy mainly formed Al₃Sc particles,resulting in grain refinement and dispersion.At the same time,the generated Al₃Cu₄Sc distribution in the grain boundary improved the performance of the alloy organization;lanthanum alloy mainly formed Al₇CuLa₂phase which dispersed in the grain boundary and improved the microstructure and properties of alloy.3.Under the same heat treatment system,the improvement of grain roundness and mechanical properties of the alloy was more significantly improved by the addition of Sc element compared with La element,which showed that the microstructure and mechanical properties of the alloy could be more improved by Al₃Sc compared with Al₇CuLa₂.