Study On Aging Precipitate And Plastic Deformation Behavior Of Mg-Y-Nd Alloy

In the present work, comprehensive characterization techniques including Optical Microscope (OM), X-Ray Fluorescence (XRF), Differential Scanning Calorimeter (DSC), X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS), Electron Backscatter Diffraction (EBSD) and Transmission Electron Microscope (TEM) were employed to study the ageing hardening behavior of Mg-Y-Nd alloy and reveal the morphology, structure of the precipitates and their orientation relations with matrix. Moreover, the effects of initial texture and the precipitates on deformation behavior and on microstructure and texture evolution were investigated and discussed. The main results are as follows:①The internal defect structure has been removed after extrusion and hot rolling processing. The grain of the alloy was significantly refined by extrusion and a (0001) fiber texture was formed. However, coarse grain was found after hot-rolling and annealing, and a (0001) basal texture was formed.②The ageing hardening effect was most significant at 210℃and a maximum hardness of 139 Hv was obtained after 59 h. And the corresponding yield strength and tensile strength reached 292Mpa and 347Mpa, respectively. The improvement of hardness and strength was not obvious after 46 h of ageing at 150℃, and the ductility was seriously reduced. A maximum hardness was obtained after 8 h of ageing at both 250℃and 280℃. The strength of the peak-aged alloy at these temperatures was not significantly improved.③The peak-aged alloy at 150℃contained well-dispersed fineβ''(Mg3Y0.85Nd0.15) precipitates, and the orientation relation betweenβ''precipitates and the matrix was: . the peak-aged alloy at 210℃contained well-dispersed findβ'(Mg12NdY) precipitates and the orientation relation betweenβ'precipitates and the matrix was:. Coarseβ1 andβ(Mg14Nd2Y) precipitates were found in the peak-aged alloys at 250℃and 280℃.④Tension twin was observed in the Mg-Y-Nd alloy after compression deformation. The initial texture and precipitates had significant effects on twinning. More twinning was observed in the samples with C//ED than that with C⊥ED. The amount of twinning was decreased with the presence of precipitates for aged samples compared to the extruded samples with the same initial texture. However, the softening phenomenon at the stress-strain curve due to twinning was less significant in comparison with that observed in AZ series magnesium alloys.