Effects Of Al And Rolling Process On Microstructure And Mechanical Properties Of Mg-Y-Nd Alloys

Magnesium rare earth alloy is widely used in aviation,aerospace and other fields because of its low density and high strength.This paper aims to prepare Mg-Y-Nd-Al alloy sheets with low cost and high performance.The effects of Al on the microstructure and mechanical properties of as-cast,as-homogenized and as-rolled alloys were studied by adjusting the content of Al.On this basis,the microstructure and properties of the alloy sheets under different rolling processes（total deformation and rolling temperature）were further studied,and the rolling process parameters were optimized.It provides a reference for preparing high-performance and low-cost magnesium rare earth alloy sheets.The main research results are as follows:The grain size of as-cast Mg-4Y-3Nd-x Al（x=0,0.5,1.0,1.5 wt.%）alloy gradually decreases with Al content,and the second phases in the alloy microstructure mainly include the Mg₅RE phase and the Al₂RE phase.After homogenization,the Al₂RE phase does not dissolve,while the Mg₅RE phase dissolves;the grain size of the Mg-4Y-3Nd alloy without Al addition increased significantly,while the grain size of the alloy refined by Al increased slightly,showing good grain thermal stability.After homogenization treatment,the mechanical properties of Mg-4Y-3Nd-1.5Al alloy are the best,and the tensile strength,yield strength and elongation are 196.4 MPa,132.4MPa and 15.9%,respectively.After hot rolling treatment,the Al₂RE phase in the alloy was uniformly distributed and the morphology did not change significantly,while the dynamic Mg-RE phase precipitated in the grain.The Al₂RE phase can promote dynamic recrystallization（DRX）by the particle excitation nucleation（PSN）mechanism.With the increase of Al content,the number of Al₂RE phases in the alloy increases,the DRX degree increases,the grains are refined,the texture strength decreases,and the mechanical properties of the alloy increase.The mechanical properties of rolled Mg-4Y-3Nd-1.5Al alloy are the best,and its tensile strength,yield strength and elongation after fracture are 264.7 MPa,225.5 MPa and 9.4%,respectively.With the increase of the total deformation,the DRX degree is improved,the grain size is obviously refined,and the strength of the plate is improved,but the plasticity is reduced.The comprehensive mechanical properties of the plate with 60%total deformation are the best.With the increase of rolling temperature,the work hardening effect of the plate decreases,but the forming ability increases,the recrystallized grains grow,the strength of the plate decreases,but the plasticity increases.When the rolling temperature is 440°C,the mechanical properties of the sheet are the best,and the tensile strength,yield strength and elongation are 274.9 MPa,260.5 MPa and 8.7%,respectively.