Investigation On Anisotropy Of Extrusion-rolling Sheet Of Mg-Gd-Zr Alloy

As the lightest commercial metal material, magnesium alloys have many advantages such as high specific strength, high specific stiffness. It is promising to be widely used in aerospace, automobile and electronic and other fields. However, because of the poor formability at room temperature, the traditional rolling must be conducted at a higher temperatures. The production sequence of magnesium alloy in hot rolling is complicated and costly.VK alloy sheets were prepared by extrusion and rolling in research. The appropriate extrusion and rolling parameters were determined in experiments. optical microscopy, X-ray fluorescence spectroscopy, X-ray diffraction analysis, tensile testing were employed to investigate the microstructure,texture,and mechanical properties changes during extrusion, rolling and heat treatment. The main research contents and results are as follows:① A refine structure was obtained by extrusion at the temperature of 420℃ with extrusion ratio of 123 in VK2 a and VK4 a alloys, however, the average grain size in middle was not the same as that on the sides. The finer extrusion structure has been produced by means of adding more alloying element. Average grain sizes are 20 μm and 25 μm in edge and middle VK2 a extrusion plates, respectively. The corresponding values for VK4 a are 8.3 μm and11.5 μm. There is strong basal texture in the extruded and annealing treatment VK2 a and VK4 a alloy, basal texture intensities of 9.2 and 11.0 were obtained for extruded VK2 a and VK4 a. The IPA of yield strength, tensile strength and elongation for extruded VK2 a alloy are 15.8%, 2.8%, 12.6%, respectively. 37.0%, 6.9% and 26.9% are the corresponding values for VK4 a. Extruder VK2 a alloy shows less anisotropy than VK4 a.② When extrusion temperature increases to 440℃ and extrusion ratio drops to 32, average grain size in extruded VK2 b alloy is 10.4 μm, which is smaller than the VK2 a alloy. Extrusion stringers can be easily observed along the extrusion direction. The IPA of yield strength, tensile strength and elongation for extruded VK2 b alloy are 9.3%,14.0% and 14.6%,respectively.③ Different rolling methods are applied in extrusion VK2 b alloy including unidirection rolling, cross rolling I and cross rolling II. Basal texture existed in all rolled sheet, which decreases from 12.8 in initial sheet to 10.5, 5.0, 5.3, respectively. The texture intensity is enhanced with the increase of annealing time in 350℃,while texture types remains.