Titanium alloys are widely employed in aerospace applications due to an outstanding combination of properties. The variety of loading conditions and microstructures encountered in industrial components is urging the development of microstructure sensitive modeling capabilities. In particular, reliable predictions require a good knowledge of operating deformation mechanisms. The present study aims at providing a thorough characterization of deformation mechanisms in the near-α Ti-6Al-2Sn-4Zr-2Mo alloy using experiments and simulations. The sequential activation of deformation mechanisms in the α phase was monitored in situ during a tensile test carried out in a scanning electron microscope using a combination of slip traces analysis and electron back-scattered diffraction. Basal slip is activated first, and prismatic slip activity, which proceeds at a higher macroscopic stress level, is needed for a significant creep/relaxation to occur. While little evidence of 〈〉-type pyramidal slip was found, 〈 + 〉 pyramidal slip involved first-order pyramidal planes and operates at stress levels near or above the 0.2% proof stress. Atomic force microscopy characterization of the features of the different slip modes revealed that 〈〉 slip is coarser and wavier than 〈 + 〉 slip. Twinning, which is usually neglected in such alloys within this strain regime, was observed to be slip stimulated at a plastic strain as low as 0.5%. Crystal plasticity parameters leading to an accurate simulation of the activation sequence of deformation mechanisms were then determined. For this purpose, critical resolved shear stress values were derived for the different slip and twinning modes using specific approaches and subsequently validated using crystal plasticity simulations based on fast-Fourier transforms.

中文翻译：

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Ti-6Al-2Sn-4Zr-2Mo 钛合金 α 相的变形机制：原位实验与模拟

钛合金因其出色的性能组合而广泛应用于航空航天领域。工业部件中遇到的各种载荷条件和微观结构正在推动微观结构敏感建模能力的发展。特别是，可靠的预测需要充分了解运行变形机制。本研究旨在通过实验和模拟来全面表征近α Ti-6Al-2Sn-4Zr-2Mo 合金的变形机制。在扫描电子显微镜中进行拉伸测试期间，结合滑移痕迹分析和电子背散射衍射，对 α 相变形机制的顺序激活进行了原位监测。基底滑移首先被激活，并且在较高宏观应力水平下进行的棱柱滑移活动是发生显着蠕变/松弛所必需的。虽然几乎没有发现 <> 型金字塔滑移的证据，但 <+> 金字塔滑移涉及一阶金字塔平面，并且在接近或高于 0.2% 屈服强度的应力水平下工作。不同滑移模式特征的原子力显微镜表征表明，<>滑移比<+>滑移更粗糙且更波动。孪生在这种应变范围内的此类合金中通常被忽略，但据观察，在低至 0.5% 的塑性应变下，孪晶会受到滑移刺激。然后确定了能够准确模拟变形机制激活序列的晶体塑性参数。为此，使用特定方法导出了不同滑移和孪生模式的临界解析剪切应力值，并随后使用基于快速傅立叶变换的晶体塑性模拟进行了验证。