Two phase titanium alloys are important for high‐performance engineering components, such as aeroengine discs. The microstructures of these alloys are tailored during thermomechanical processing to precisely control phase fractions, morphology and crystallographic orientations. In bimodal two phase (α + β) Ti‐6Al‐2Sn‐4Zr‐2Mo (Ti‐6242) alloys there are often three microstructural lengthscales to consider: large (∼10 μm) equiaxed primary α; >200 nm thick plate α with a basketweave morphology; and very fine scaled (<50 nm plate thickness) secondary α that grows between the larger α plates surrounded by retained β. In this work, we utilise high spatial resolution transmission Kikuchi diffraction (TKD, also known as transmission‐based electron backscatter diffraction, t‐EBSD) and scanning electron microscopy (SEM)‐based forward scattering electron imaging to resolve the structures and orientations of basketweave and secondary α in Ti‐6242. We analyse the α variants formed within one prior β grain, and test whether existing theories of habit planes of the phase transformation are upheld. Our analysis is important in understanding both the thermomechanical processing strategy of new bimodal two‐phase titanium alloys, as well as the ultimate performance of these alloys in complex loading regimes such as dwell fatigue. Our paper champions the significant increase in spatial resolution afforded using transmission techniques, combined with the ease of SEM‐based analysis using conventional electron backscatter diffraction (EBSD) systems and forescatter detector (FSD) imaging, to study the nanostructure of real‐world engineering alloys.

中文翻译：

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使用透射菊池衍射表征 α+β 钛合金中的 α 变体

两相钛合金对于高性能工程部件很重要，例如航空发动机盘。这些合金的微观结构在热机械加工过程中经过调整，以精确控制相分数、形态和晶体取向。在双峰两相 (α + β) Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) 合金中，通常需要考虑三个显微结构长度尺度：大（~10 μm）等轴初生 α；> 200 nm 厚的板 α，具有篮织形态；和非常精细的（<50 nm 板厚度）次生 α，它在被保留 β 包围的较大 α 板之间生长。在这项工作中，我们利用高空间分辨率透射菊池衍射（TKD，也称为基于透射电子背散射衍射，t-EBSD) 和基于扫描电子显微镜 (SEM) 的前向散射电子成像，以解析 Ti-6242 中篮织和次生 α 的结构和方向。我们分析了在一个先验 β 晶粒内形成的 α 变体，并测试了相变习性平面的现有理论是否得到支持。我们的分析对于理解新型双峰双相钛合金的热机械加工策略以及这些合金在诸如停留疲劳等复杂载荷状态下的最终性能都很重要。我们的论文支持使用透射技术显着提高空间分辨率，结合使用传统电子背散射衍射 (EBSD) 系统和前散射探测器 (FSD) 成像的基于 SEM 的分析的简便性，