Tailoring The Texture And Anisotropy Of A Mg-2Zn-2Gd Alloy Plates By Cross Rolling

A cross rolling was developed as an effective way to tailor the texture and improve the formability of Al plates. In recent years, some researchers also tried to use this cross rolling process to tailor the strong basal texture of Mg alloys. Unfortunately, obvious reorientation of the basal poles did not appear. It was reported that addition of Gd, Ce was very effective for developing a more random texture in hot-worked Mg alloys. Double peaked textures with basal poles largely tilting from the ND toward the TD often form in hot-rolled or annealed plates, which present intensive planar anisotropy. In the present study, we designed a Mg-2Zn-2Gd(wt%) alloy and proposed to apply cross rolling on this kind of paltes to tailor the texture. Combining the usage of many advanced characterization techniques(e.g. EBSD and XRD) and mechanical property tests(e.g. tensile and Erichsen test), the formation mechanism of texture during cross rolling and subsequent annealing, the texture memory effect of hot cross-rolled texture, and the relationships between the texture distribution and forming ability were systematically investigated. The projects lay great emphasis on disclosing the mechanism of rolling direction affecting deformation microstructure and crystallographic orientation of recrystallized grains.The results show that:(1) Cross rolling followed by annealing develops a texture with(0002) poles evenly distributed on a circle about 40° away from the ND. Finally, a completely removed planar anisotropy was achieved. It can be inferred that cross rolling can be an effective method to tailor the texture distribution and anisotropy of the Mg alloys plates with basal pole largely away from the ND.(2) The present study shows that varying the rolling path greatly changes the rolling and the annealing textures of Mg-2Zn-2Gd plate. The textures distribute along the direction parallel to the rolling path after cold rolling, while appear along the direction perpendicular to the rolling path afterannealing. Rolling path rather than orientations of deformed grains determines orientations of the recrystallized grains. The nuclei of recrystallized grains with basal poles distribution perpendicular to the rolling path have a clear advantage over the other ones. This is the reason for formation of texture in the annealed plates.(3) Hot cross rolling and annealing treatment was applied on a homogenized Mg-2Zn-2Gd alloy plate. It was found that the hot cross rolling stage greatly affects the annealing texture whose basal poles distributing on a circle largely away from the ND. However, the annealing texture of cross rolling could not reserve after subsequent unidirectional hot rolling and annealing, namely the texture memory effect does not exist.(4) Mechanical property tests show that for the annealed plate with double peaked textures, there is a great difference in yield strength along different directions. Yield strength along the RD is about 31 MPa higher than that along the TD in RD30% annealed plate. However, for the cross-rolled plate with basal poles distributing on a circle largely away from the ND, the anisotropy of yield strength was removed and the ?r was reduced. In Erichsen test, the cross-rolled plate shows a slightly higher IE value than RD-rolling, indicating a better formality.