Abstract Relatively low levels of inter-pass deformation have been found to be very effective in refining the coarse columnar grain structures normally seen in Ti-6Al-4V components, built using wire-fed high-deposition-rate additive manufacturing processes. The most important process parameters that control the level of β recrystallization – the final grain size and micro-texture – were systematically investigated by simulating the deformation and high heating rate conditions in controlled samples, to develop the process knowledge required to optimise inter-pass deformation and obtain predictable grain sizes. Overall, it was found that the level of β-grain refinement achieved by inter-pass deformation was surprisingly insensitive to the ranges of deformation temperatures, deformation speeds, and changes to the as-deposited α + β microstructure, expected within the WAAM process window, provided a minimum plastic strain of only 14% was achieved in each added layer. Conversely, the final component grain size was shown to be strongly affected by rapid grain growth on re-heating above the β transus. The texture results obtained were consistent with previous work which suggested that, with fine AM transformation microstructures, new β-grain orientations may be produced during the α → β transformation from the development of twinning faults, induced by the prior deformation and rapid heating. In contrast, greatly increasing the starting α lamellar spacing – to be more similar to that found in a wrought material – greatly reduced the level of recrystallization and also appeared to change the recrystallization mechanism to favour new β orientations produced largely by local lattice rotation.

中文翻译：

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层间变形Ti-6Al-4V线弧增材制造工艺参数对快速加热β再结晶的影响

摘要 相对较低的层间变形水平对于细化通常出现在 Ti-6Al-4V 组件中的粗柱状晶粒结构非常有效，这些组件使用送丝高沉积速率增材制造工艺制造。通过模拟受控样品的变形和高加热速率条件，系统地研究了控制 β 再结晶水平的最重要工艺参数——最终晶粒尺寸和微观结构，以开发优化层间变形所需的工艺知识并获得可预测的晶粒尺寸。总的来说，发现通过层间变形实现的 β 晶粒细化水平对变形温度范围、变形速度和沉积态 α + β 微观结构的变化非常不敏感，预计在 WAAM 工艺窗口内，只要在每个添加层中实现的最小塑性应变仅为 14%。相反，最终组分的晶粒​​尺寸被证明受 βtransus 上方重新加热时快速晶粒生长的强烈影响。获得的织构结果与先前的工作一致，这表明，对于精细的 AM 转变微观结构，在由先前变形和快速加热引起的孪生断层发展的 α → β 转变过程中可能会产生新的 β 晶粒取向。相比之下，大大增加起始 α 层状间距 - 更类似于在锻造材料中发现的间距 - 大大降低了再结晶水平，并且似乎也改变了再结晶机制，以有利于主要由局部晶格旋转产生的新 β 取向。