Effects of Extrusion Ratio on the Microstructure, Texture and Mechanical Properties of Mg-2.5Nd-0.5Zn-0.5Zr Alloy Sheets

The effects of different extrusion ratios (7.6, 12.5 and 26.1) on the microstructure evolution, texture characteristics and mechanical properties of Mg-2.5Nd-0.5Zn-0.5Zr (wt.%) alloys have been systematically studied. The results showed that with the increase of extrusion ratio, the dynamic recrystallization grain size decreased first and then increased, the texture state changed from weakened bimodal texture to strong basal texture with the texture strength increased from 6.7 to 19.4. The growth of grain size was mainly attributed to rise of temperature transformed by the deformation heat with high extrusion ratio and the more intense extrusion deformation. The mechanical properties of the alloy increased first and then decreased with the increase of the extrusion ratio. When the extrusion ratio was 12.5, the alloy exhibited excellent mechanical properties. The higher yield strength results from the interaction of refinement strengthening, dislocation strengthening, precipitation strengthening and texture strengthening. With the increase of extrusion ratio, the proportion of basal slip increased gradually when the alloy was tensile in extrusion direction, and the deformation mechanism was mainly basal slip. When the alloy was tensile along the transverse direction, the proportion of basal slip decreased, and the proportion of prismatic slip increased gradually. The main deformation mechanism were basal slip and prismatic slip.