Deformation Behavior, Microstructure and Microhardness of Mg-3Al-1Zn Microtubes Processed by Isothermal Micro-Backward Extrusion

摘要

In the present work, for the first time, the capability of isothermal micro-backward extrusion method for fabrication of microtubes of coarse-grained as-cast AZ31 magnesium alloy was confirmed. Macrographs of the fabricated microtubes showed no visible surface cracks and acceptable dimensional accuracy. Microstructural investigations of the microtube revealed inhomogeneous microstructure consisting of a non-uniform distribution of shear bands and dynamically recrystallized grains. Microhardness measurements showed considerable enhancement compared with the as-received material due to the formation of shear bands and grain refinement inside them. Moreover, microhardness measurements revealed inhomogeneous mechanical properties of the microtube. Deformation behavior was investigated by finite element simulation using conventional material model. True stress-strains data extracted from experimental micro-compression test were used as the material parameters for finite element simulation. As a result, the regions with the highest material flow were found to be in the vicinity of the radius of the punch. Comparing this result with microstructural investigations showed that these regions had the highest density of shear bands and dynamically recrystallized grains.