Microstructure and texture evolution of Mg–7Y–1Nd–0.5Zr alloy sheets with different rolling temperatures

Abstract

The extruded Mg–7Y–1Nd–0.5Zr (wt%) alloy were performed to the same strain hot rolling with different temperatures. The microstructure and texture evolution of the sheets were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and electron back-scattered diffraction (EBSD). The results indicate that the microstructure becomes homogeneous after hot rolling process and precipitated phase distributes at grain boundaries along rolling direction. With the increase in rolling temperature, the grains of sheet grow up. The sheet rolling at 400 °C is composed of recrystallization grains, the necklace of the precipitated phase in the grain boundaries and excessive dislocations. The structure of necklace of the precipitated phase is fcc structure with lattice constant of a = 0.75 nm. With rolling temperatures increasing from 400 to 450 °C, the content of recrystallized grains in volume fraction with relatively random orientations increases significantly. Compared with the rolling process at 400 °C, the amount of precipitated phases is reduced at the grain boundary, and the precipitated phase begins to appear in the grain interior when rolling at 450 °C. The structure of the precipitated phase is fcc with lattice constant of a = 2.22 nm. The recrystallization grains begin to grow in the rolling process at 500 °C. The basal texture is obviously produced during the rolling process at 400 and 450 °C; however, the basal texture is weak in the rolling process at 500 °C. The pole point of the (0002) pole figure is concentrated in the center. It can be seen that the basal surface is parallel to RD–TD surface of the rolling sheets. Compared with as-extruded alloy, the basal texture is significantly enhanced with a small increase in basal texture intensity from 6.127 to 7.175, and $$(10\bar{1}0)$$ and $$(11\bar{2}0)$$ textures change to random textures.