钐添加对挤压态Mg-9Gd-0.5Zr合金动态再结晶的抑制及时效析出的促进作用OA

The effects of samarium(Sm)additions(mass fraction,0%,1%,and 2%)on the microstructures and mechanical properties of as-extruded Mg-9Gd-0.5Zr alloys were systematically investigated using methods including scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),transmission electron microscopy(TEM),and tensile testing.The results show that all three alloys exhibit a bimodal microstructure.Sm addition weakened the texture intensity of the<01-10>orientation in non-recrystallized regions,effectively suppressed dynamic recrystallization(DRX),and caused the volume fraction of DRXed regions to gradually decrease with increasing Sm content.Specifically,the volume fraction in the Mg-9Gd-2Sm-0.5Zr alloy decreased by 22.91%compared to the Sm-free alloy.Dynamic precipitates in DRXed regions,identified as the Mg5 RE phase by TEM characterization,were promoted in formation and growth by Sm addition.This altered the nucleation sites of precipitates in peak-aged non-recrystallized regions,increasing their number density and aspect ratio.Mechanically,Sm addition enhanced the yield strength of as-extruded samples.The Mg-9Gd-1Sm-0.5Zr alloy exhibited the best performance,with a tensile yield strength(TYS)of 446 MPa and a tensile elongation to fracture(TEL)of 6.98%.The study confirmed that the yield strength of the Mg-9Gd-0.5Zr and Mg-9Gd-1Sm-0.5Zr alloys primarily originated from the combined strengthening effects of precipitation strengthening and grain refinement strengthening.