不同锤锻方式下Ti-6Al-4V合金组织及取向演变

Microstructure and texture evolution in Ti-6Al-4V alloy under different hammer forging processes

利用扫描电镜和背散射衍射技术研究了Ti-6Al-4V合金在不同锤锻变形方式下的组织与取向变化.结果显示:随着镦拔变形次数的增加,Ti-6Al-4V合金中α相及β相组织均趋于均匀,而且两相的取向聚集越不明显;进一步热处理后,锻造过程中形变储存能得到释放,在释放过程中两相也会发生一定的倾转,轴向三次镦拔或者换向三次镦拔对组织均匀性改善明显.综合分析发现,密排六方结构的α相的取向分布对变形方式较敏感:原始棒材以及一次镦拔时,合金中α相的取向{0001}基面织构占了很大部分;随着镦拔次数增多,形变能增加,虽然{0001}基面滑移被抑制,但是{1010}、{1120}等柱面滑移以及{0111}、{1123}等锥面滑移得以开动,大幅地增加了取向的种类,进而降低了取向的集中性,使得取向更趋均匀化.

Microstructure and texture evolution in Ti-6Al-4V alloy under different hammer forging processes were investigated by electron backscattered diffraction and scanning electron microscopy. The results showed that the inicrostructure became more and more uniform along with the frequency of forging, and the directionality turned more and more invisible ; after heat treatment, the distribu- tion uniformity of α and β phases and the micro-texture were both increased to somewhat extent because of the release of deformation energy and the tilting of α and β phases, especially highlighted in the forging modes of uniaxial 3 times and cross upsetting and stretching 3 times. As for the texture distribution of this alloy, the close-packed hexagonal structured α phase was more sensitive to hot working modes than the body centered α phase. For raw materials and one-time axial upsetting and stretching, the texture of α phase mainly consisted of the {0001 } basal texture; with the increase of frequency and deformation energy, the {1010} and {1120} prismatic slip and the { 1011t and {12121 pyramidal slip were strengthened, accordingly inducing the more uniform of orientation because of the texture components and the dispersion of texture distribution.