Revealing flow patterns in fusion welding with stereo X-ray imaging.

熔焊是金属合金中应用最广泛和最突出的连接方法之一。人们普遍认为，在凝固过程中，熔池内的流动对焊缝区域形状、显微组织、缺陷和由此产生的残余应力有显著影响。然而，目前还没有可靠的金属合金焊池内流动的实验数据，科学的理解依赖于缺乏适当验证的简化模型和模拟。因此，本提案的目标是实时获得液态金属流动的三维可视化（即4D）量化，以分析焊接池中不断变化的流动。研究结果将指导、验证和完善焊接池模型，科学的理解将使焊接工艺得到改进。提出了一种独特而新颖的实验配置，用于在英国钻石光源的原位焊接模拟实验中实现时间分辨立体x射线成像。通过使用x射线光学拆分常规同步加速器光束获得的两个相互倾斜的x射线光束的实验配置将有助于实现立体成像能力。嵌入焊缝材料（焊池中）的高x射线衰减小颗粒将作为跟踪流体流动模式演变的标记。通过定制的图像处理和分析程序，结合在这种立体配置中记录的两组时间分辨率图像，将呈现4D可视化和流动的时空量化，从而能够分析不断变化的焊接池中的流动。

Fusion welding is one of the most widely used and prominent joining methods for metallic alloys. It is well accepted that flow within the weld pool significantly influences weld region shape, microstructure, defect and resulting residual stress formation during solidification. However, there are no reliable experimental data on flow within metallic alloy weld pools and scientific understanding is reliant on simplified models and simulations that lack proper validation. Hence, the objective of this proposal is to acquire 3D visualisation in real time (i.e. 4D) quantification of the liquid metal flow to analyse evolving flow in weld pools. The results will guide, validate and qualify weld pool modelling and the scientific understanding will enable improvements in the weld processes. A unique and novel experimental configuration is proposed to realise time-resolved stereo X-ray imaging for in situ weld simulation experiments at the Diamond Light Source, UK. An experimental configuration, with two mutually inclined X-ray beams, which are obtained through splitting the regular synchrotron beam using X-ray optics, will be instrumental in realising the stereo imaging capability. Small, high X-ray attenuating particles embedded in the weld materials (in weld pool) will serve as markers to track the evolving fluid flow patterns. Combining the two sets of time-resolved images recorded in this stereo configuration, via bespoke image processing and analysing procedures will render 4D visualisation and spatio-temporal quantification of flow, enabling analysis of flow in evolving weld pools.