热变形及热处理过程中TC17钛合金组织与取向的关联性

Correlation between structure and orientation of TC17 titanium alloy during thermal deformation and heat treatment

为了进一步研究热压缩及热处理过程对组织及取向变化的关联性,通过对TC17进行热压缩变形及后续热处理,利用光学显微镜和背散射电子衍射等分析方法,结合晶粒尺寸、织构分布图、极图以及反极图,研究变形后及热处理后的TC17的组织结构、晶粒尺寸的变化和取向的演变规律以及两者之间的关联性.结果表明:随着变形温度升高,初生α相含量大幅减小,尺寸减小,大部分α相晶粒分散分布,且位于高温β相晶粒的三叉晶界上;热处理后,α相和β相组织特征清晰,界限明显,初生α相依旧存在,且趋于等轴化,亚稳定β相发生转变,形成片层状β转变组织;热变形使α相织构极密度值减小,且随之温度增加,α相织构极密度值也变小;热变形后的α相已不存在明显的强织构,热变形对α相晶粒的取向影响较大,很明显的改善了其取向的均匀性;热变形同样使β相织构极密度值减小,但效果不明显.β相仍存在取向集中现象,取向均匀性相对较差.

In the previous studies on the microstructure and orientation of titanium alloys,the microstructural and orientational evolution of typical titanium alloys during thermal compression have been studied in depth.However,studies of the correlation between hot compression and heat treatment processes on microstructural and orientational changes have been few.It is of great significance to further study this correlation during hot treatment.For this study,during hot compression deformation and subsequent hot treatment of TC17 titanium alloy on a thermal simulator using cylindrical specimens,the microstructure,grain size change,and orientation evolution of TC17 were studied using optical microscopy and backscattered electron diffraction analysis.Grain size,texture distribution,pole figure,and reverse polarity were analyzed.Law and the relation between structure and orientation results show that the primaryα-content decreases dramatically and size decreases in tandem with deformation temperature.Most of theαphase grains are dispersed and located on the trigeminal grain boundaries of the high temperatureβphase grains.After heat treatment,theαphase andβphase had a clear structure and distinct boundary.The primaryαphase still exists and tends to be equiaxed,and the metastableβphase changes formed a lamellarβ-transformed structure.The hot deformation reduces the density of theαphase texture.Additionally,with increasing temperature,the density value of theαphase texture also becomes small.Theαphase is no longer strongly textured after thermal deformation,and the orientation of theαphase grains is considerably influenced by thermal deformation,which clearly improves the uniformity of orientation.The thermal deformation also reduces the texture polar density value of theβphase,but the effect is not obvious.However,there is still a density of orientation,and the uniformity of the orientation is relatively poor.