This study investigates the impact of notch severity and initial texture on the micro-mechanisms during low strain deformation in commercially pure Titanium, exploiting in-situ electron back scatter diffraction (EBSD) experiments and crystal plasticity finite element model (CPFEM). In-situ tests were performed at different strain steps of un-notched and notched samples of transverse direction (TD) and rolling direction (RD) orientations. CPFEM, based on initial EBSD microstructures, predicted profuse prismatic slip traces and early activation of prismatic slip in notched sample, with RD orientation exhibiting higher activity. Further, CPFEM results revealed early activation of high CRSS slip systems as well as evidence of early twin activity at notch tip due to severely localized plastic deformation and steep strain gradient, as observed by GND maps causing higher stress at grain boundaries. At the notch tip, digital images correlation (DIC) at microscale indicated strain localization at and to the tensile axis for TD and RD orientations, respectively. Furthermore, 2.5D and 3D CPFEM confirmed distinct strain patterns at notch tip: TD orientation exhibited combined basal and prismatic slip influences, while RD orientation displayed dominant prismatic slip systems at localized strain. The model also successfully predicted anisotropic surface roughness, contributing to early necking in RD orientation.

中文翻译：

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商业纯钛存在缺口时各向异性变形的微观机制：利用 CPFEM 模拟进行的原位研究

本研究利用原位电子背散射衍射 (EBSD) 实验和晶体塑性有限元模型 (CPFEM)，研究了商业纯钛低应变变形过程中缺口严重程度和初始织构对微观机制的影响。对横向（TD）和轧制方向（RD）取向的无缺口和缺口样品的不同应变步骤进行了原位测试。基于初始 EBSD 微观结构的 CPFEM 预测了缺口样品中的大量棱柱滑移痕迹和棱柱滑移的早期激活，其中 RD 方向表现出更高的活性。此外，CPFEM 结果揭示了高 CRSS 滑移系统的早期激活，以及由于严重的局部塑性变形和陡峭的应变梯度而导致缺口尖端早期孪晶活动的证据，如 GND 图所观察到的，导致晶界处更高的应力。在缺口尖端，微尺度的数字图像相关 (DIC) 分别表明 TD 和 RD 方向的拉伸轴上的应变局部化。此外，2.5D 和 3D CPFEM 证实了缺口尖端处的不同应变模式：TD 方向表现出基础和棱柱滑移的综合影响，而 RD 方向则显示局部应变下占主导地位的棱柱滑移系统。该模型还成功预测了各向异性表面粗糙度，有助于 RD 方向的早期颈缩。