Superplastic behavior of a fine-grained Mg-Gd-Y-Ag alloy processed by equal channel angular pressing  

作　　者：A.Rezaei R.Mahmudi R.E.Logé 

机构地区：[1]School of Metallurgical and Materials Engineering,College of Engineering,University of Tehran,Tehran 14395-515,Iran [2]Laboratory of Thermomechanical Metallurgy-PX Group Chair,Ecole Polytechnique Fédérale de Lausanne(EPFL),CH-2002 Neuchâtel,Switzerland

出　　处：《Journal of Magnesium and Alloys》2023年第10期3815-3828,共14页镁合金学报（英文）

摘　　要：An extruded Mg-6Gd-3Y-1.5Ag(wt%) alloy was processed by 6 passes of equal channel angular pressing(ECAP) at 553 K using route Bc to refine the microstructure. Electron back-scattered diffraction(EBSD) analysis showed a fully recrystallized microstructure for the extruded alloy with a mean grain size of 8.6 μm. The microstructure of the ECAP-processed alloy was uniformly refined through dynamic recrystallization(DRX). This microstructure contained fine grains with an average size of 1.3 μm, a high fraction of high angle grain boundaries(HAGBs), and nano-sized Mg_(5)Gd-type particles at the boundaries of the DRXed grains, detected by transmission electron microscopy(TEM). High-temperature shear punch testing(SPT) was used to evaluate the superplastic behavior of both the extruded and ECAP-processed alloys by measuring the strain rate sensitivity(SRS) index(m-value). While the highest m-value for the extruded alloy was measured to be 0.24 at 673 K, the ECAP-processed alloy exhibited much higher m-values of 0.41 and 0.52 at 598 and 623 K, respectively,delineating the occurrence of superplastic flow. Based on the calculated average activation energy of 118 kJ mol^(-1) and m-values close to 0.5, the deformation mechanism for superplastic flow at the temperatures of 598 and 623 K for the ECAP-processed alloys was recognized to be grain boundary sliding(GBS) assisted by grain boundary diffusion.

关 键 词：Mg-Gd-Y alloys Equal channel angular pressing SUPERPLASTICITY Strain rate sensitivity Grain boundary sliding 

分 类 号：TG379[金属学及工艺—金属压力加工]