Microstructure and Property Relationship Controllable by Thermomechanical Processing of Mg-Al-Zn-Y-Ca Alloy Sheets

The influence of thermomechanical processing on the microstructure and texture evolution is examined in the present study using an AZ31 alloy modified by Ca and Y addition. AZXW3100 alloy sheets were produced by hot rolling at two different temperatures of 450 degrees C and 500 degrees C. Changes in the deformation degree per pass at each rolling temperature were used to analyze the effect of process condition. The sheet rolled at 450 degrees C and the deformation degree per pass decreasing from 0.3 to 0.1 with rolling step shows a relatively strong texture with a basal pole split into the sheet rolling direction. On the contrary, the sheet rolled at 450 degrees C and deformation degree per pass increasing with rolling step from 0.1 to 0.3 shows a significantly weak texture with basal pole split into the rolling direction and the transverse direction. The sheets rolled at 500 degrees C show a further distinct texture type in which the basal poles are largely tilted into the rolling direction. The rolling condition influences also on the grain sizes in the recrystallized sheets, varying within a range of 6 mu m and 21 mu m after annealing at 400 degrees C for 10 min of the differently rolled sheets. The sheet formability is dependent on the texture sharpness, i.e. the weaker texture the higher formability. The sheet rolled at 450 degrees C with the increase of deformation degree per pass with the rolling step shows an excellent formability with the Erichsen Index of 8.1, which is about 3 times higher value than that obtained for a conventional Mg alloy sheet.