Effect Of Lanthanum And Cerium Contents On Microstructure And Properties Of AE44 Magnesium Alloy

Mg-Al-RE(Rare Earth)alloys are one of the die-casting magnesium alloy families developed for high temperature applications.They can be used in environments with temperatures more than 150°C such as automotive powertrains with operating temperatures up to 200°C.Among AE series magnesium alloys,AE44 rare earth magnesium alloy has attracted wide attention due to its good combination of strength and ductility.In recent years,many scholars have done a lot of research.Traditional AE44 magnesium alloys are mostly prepared by using cerium-rich(La Ce Pr Nd)mixed rare earth as raw materials,which not only increases material costs,but also is not conducive to the sustainable development of rare earths.The research in this article is to prepare AE44 rare earth magnesium alloys with different lanthanum cerium contents by using cheap lanthanum cerium rare earths,and compare the effects of different contents of lanthanum cerium rare earths on the microstructure and mechanical properties of as-cast and extruded AE44 magnesium alloys.In this paper,four kinds of AE44 magnesium alloys with different lanthanum and cerium contents were prepared in a crucible furnace using Ar + SF6 gas protection.Instron-5982 universal testing machine,X-ray diffraction(XRD),Electron backscatter diffraction technology(EBSD)and other experimental methods were used to analyze the microstructure,mechanical properties of as-cast AE44 magnesium alloys and extruded AE44 magnesium alloys.The as-cast AE44 magnesium alloy AE44 magnesium alloy is based on α-Mg,the intermetallic phases mainly includes Al11RE3,Al10RE2Mn7,Al2Ce;The intermetallic phases of AE44 magnesium alloy with 1.5%La and 2.5%Ce are relatively uniform,and there are many smaller Al2 Ce phase and Al10RE2Mn7 phase.In comparison,the intermetallic phases of the AE44 magnesium alloy of other components are mostly lamellar-like,snowflake-like or rod-shaped and the grain distribution is not uniform.The tensile test results show that the AE44 magnesium alloy with 1.5%La and 2.5%Ce has the best mechanical properties,the tensile strength is 220.43 MPa,the yield strength is 82.61 MPa,and the elongation is 12.9 %.The extruded AE44 magnesium alloy structure has been significantly refined compared to the as-cast structure.The two AE44 magnesium alloys(0.5%La,3.5%Ce;1.5%La,2.5%Ce)with more Ce content have more recrystallized structureare compared with the two AE44 magnesium alloys(2.5%La,1.5%Ce;3.5%La,0.5%Ce)with more La content,but the degree of recrystallization is not sufficient,and there are a large number of dispersed ultrafine grains.Among four kinds of extruded AE44 magnesium alloys prepared in this study,AE44 magnesium alloy with a composition of 1.5%La and 2.5%Ce has the best tensile properties at room temperature and elevated temperature.The tensile strength is 282.85 MPa,the yield strength is 219.67 MPa,and the elongation is 22.08 at room temperature;The tensile strength is 168.82 MPa,the yield strength is 140 MPa,and the elongation is 43.45 at elevated temperature.The fracture mechanisms of the alloy under both room temperature and elevated temperature deformation are mainly ductile fracture.