不同初始取向TA1工业纯钛的各向异性力学行为及其塑性变形机制研究

Anisotropic Mechanical Behavior and Plastic Deformation Mechanisms of Commercially Pure Titanium with Different Initial Orientations

摘要:

以2种不同初始取向集中程度（双峰织构、分散织构）的TA1工业纯钛轧制板材为研究对象，综合运用宏观力学性能测试、微观组织表征和晶体塑性模拟等手段，系统研究了单轴加载下2种板材的应力应变曲线、拉压屈服不对称性、应变硬化、塑性应变比（r值）及织构演化等各向异性力学行为。基于考虑主导孪生系旋转的粘塑性自洽（VPSC-PTR）模型的数值模拟结果与实验结果印证性较高。双峰织构板材较分散织构板材的各向异性和拉压不对称性更为突出，且双峰织构板材在变形过程中呈现更显著的r值变化和更剧烈的织构演化。结合施密特因子分布、滑移/孪生系活性、临界分解剪切应力，阐明了初始织构对变形过程中滑移及孪生竞争协调关系的影响规律，揭示了初始取向对工业纯钛轧制板材各向异性的影响机制：柱面滑移是工业纯钛塑性变形的主导机制；双峰织构板材的拉伸孪生更易被激活，而分散织构板材的基面滑移及锥面滑移活性较高，导致2种板材呈现不同的各向异性特征；变形过程中，双峰织构板材的r值始终高于分散织构板材，柱面滑移活性降低、拉伸孪生活性增加是该现象的主导诱因。

Abstract:

The anisotropic mechanical behaviors of TA1 commercially pure titanium (CP-Ti) rolled plates with two different initial orientations (bimodal texture and dispersed texture) under uniaxial loading, including stress-strain curves, tension-compression yield asymmetry, strain hardening, plastic strain ratio (r-value), and texture evolution were investigated using macroscopic mechanical property testing, microstructural characterization, and crystal plasticity modeling. The simulation results based on the VPSC-PTR model are well agreement with the experimental data. Compared to the plate with dispersed texture, the plate with bimodal texture presents more prominent anisotropy and tension-compression asymmetry, accompanied by more significant changes in the r-value and more intense texture evolution during deformation. Combining with the Schmid factor distribution, the relative activity of slip/twinning system, and critical resolved shear stress, the effect of initial texture on competition between slip and twinning during the deformation is clarified, revealing the influence mechanism of the initial orientation on the anisotropy of the rolled CP-Ti plates. The prismatic slip is the dominant mechanism of plastic deformation in CP-Ti. And extension twinning is more easily activated in plate with bimodal texture, while basal slip and pyramidal slip are more active in plate with dispersed texture, leading to different anisotropic characteristics. Moreover, the r-value of plate with bimodal texture is higher than that with dispersed texture during deformation, which is related to the decrease in activity of prismatic slip and the increase in activity of extension twinning.