Evolution Of Microstructure And Texture Of High Purity Sheets During Cold-rolling And Annealing

With the development of titanium industry, titanium and its alloy are used widely in Aerospace, medical, automotive and other fields due to its excellent performance. The performance of high purity titanium is strongly dependent on its microstructure and texture distribution. In order to control the homogeneity of microstructure and texture of high purity titanium sheets more effectively, the different cold-rolling reduction high purity titanium sheets were used. The evolution of microstructure and texture during cold-rolling and annealing of these sheets were investigated with optical microscopy (OM), X-ray diffraction, SEM and EBSD. The main conclusion found are as follows:①Deformation comprising low-to-moderate thickness reductions(<50%) was accommodated by slip and twinning, whereas slip predominated at higher reductions.②The primary twinning systems activated were{11-22}compressive twins and {10-12}tensile twins, and the former is the main twin type.③There are two typical multiple twinning were observed: one is the co-existence of several variants of the same type of compressive twins inside individual grains; the other is the second-generation tensile twin inside primary compressive twin.④During the low-to-moderate thickness reductions deformation, twining weakens this texture component by randomizing the orientations of grains. During heavy deformation, the texture changes similar to the original state due to the absence of twinning .⑤During the annealing, the global texture of 30% cold-rolling reduction sample is maintain the bimodal distribution of basal poles. With the annealing, the <10-10>∥RD preferred orientation gradually weakened. The global texture of the 70% cold rolled high purity titanium plate exhibits a split-basal texture. The recrystallization weakens the <10-10>∥RD preferred orientation, but enhances the <11-20>∥RD preferred orientation. After annealing at 500∥, The primary recrystallization completes, and the global texture still has not significant change. However, the lager grains show stronger <11-20>∥RD preferred orientation than the smaller grains, while the smaller grains show stronger <10-10>∥RD preferred orientation. When the temperature reaches 700∥,the grains grow significantly, and the global texture changes from the spilt-basal texture to a basal texture.