[论文解读] 4D reconstruction of alumina laser melt pools at 25 kHz via operando X-ray multi-projection imaging

Lars Witte, Eliot Jermann+10 more|arXiv (Cornell University)|Mar 15, 2026

Laser-Plasma Interactions and Diagnostics被引用 0

一句话总结

引入旋转-XMPI，一种三束光学多投影XMPI方法，在探测器速率极限下实现激光熔池的4D重建，达到约25,000个重建体积/秒，相比前线 operando LPBF 成像速度提升约250倍。

ABSTRACT

Advancing additive manufacturing, e.g., laser powder-bed fusion (LPBF), requires resolving rapid processes such as melt-pool dynamics and keyhole evolution in 4D (3D + time). Operando X-ray tomography is a state-of-the-art approach for 4D characterization, but its temporal resolution is fundamentally constrained by the sample rotation speed, limiting achievable 4D imaging rates and preventing the resolution of these fast phenomena. Here we present rotation-enabled X-ray Multi-Projection Imaging (rotation-XMPI), which captures three angularly resolved projections per time step and thereby decouples temporal resolution from the sample rotation speed. Combined with a self-supervised deep-learning reconstruction framework for multi-angle inputs, rotation-XMPI enables high-fidelity 4D imaging at unprecedented speed. We demonstrate the approach in an operando alumina laser-remelting experiment at MAX IV using three beamlets combined with 25 Hz sample rotation. Rotation-XMPI resolves melt-pool morphology and keyhole evolution; in contrast, conventional and limited-angle tomography remain rotation-limited, and motion blur prevents resolving these dynamics. Overall, rotation-XMPI delivers a 250-fold increase relative to state-of-the-art melt-pool imaging, effectively achieving 25,000 reconstructed volumes per second. This method establishes a practical route to scalable ultrafast 4D imaging for additive manufacturing and other materials processes.

研究动机与目标

• 解决激光再熔融LPBF过程中的快速4D熔池动力学（3D+时间）。
• 通过多投影XMPI实现时间分辨率与样品旋转解耦。
• 开发适用于旋转-XMPI数据的自监督4D重构框架。
• 将旋转-XMPI与传统断层成像和受限角度STRT进行比较，以量化在时间和空间保真度方面的增益。

提出的方法

• 使用具备三个同步X射线束和探测器的旋转使能X射线多投影成像（rotation-XMPI）。
• 在25 kHz探测帧率下实现每个时间步的三组同时投影，同时以25 Hz旋转样品。
• 对投影进行探测器伪影、对齐、亮度归一化、去噪和Paganin相位检索等预处理。
• 将X-Hexplane 4D重构框架适配到rotation-XMPI数据，以联合重构4D相移场。
• 用归一化互相关和鲁棒性检查等方法，针对静态参考进行重构保真度评估。

Fig. 1: Acquisition setup and reconstruction results of laser remelting. a Schematic of the XMPI data-acquisition setup. Three X-ray beamlets are shown in blue and the laser in red. The sample is mounted on a rotating holder. b Photograph of the sample mounted on the holder (background grayed out) a

实验结果

研究问题

• RQ1 旋转-XMPI是否能够将时间分辨率与旋转速度解耦，以解析LPBF中的快速熔池动力学？
• RQ2 相比传统 operando 断层成像和STRT，旋转-XMPI在熔池演化的时间和空间保真度方面有何差异？
• RQ3 在使用三束同时投影与自监督重构时，能够达到的4D成像速率和空间/时间分辨率是怎样的？

主要发现

• 旋转-XMPI达到25,000个重建体积/秒，时间间隔40 μs。
• 重建体积为200 × 200 × 16体素，体素大小为4 × 4 × 4 μm^3，覆盖700个时间步，跨越28 ms。
• 三束XMPI的最大 beam间角约为47.7°，有效地将时序与旋转解耦，实现单时间步重建。
• 与传统断层成像和STRT相比，旋转-XMPI提供更高保真度，能够分辨熔池形态与空洞动力学，且不存在明显的运动模糊。
• 相对于先前的operando LPBF断层成像，在重建体积率方面实现约250倍提升（从旋转受限时间到探测器受限时间）。
• 验证表明奇偶帧子集之间的重建质量一致，与静态参考具有 reasonable 一致性。

Fig. 2: Comparison of imaging and reconstruction approaches. a,b Schematics of rotation-XMPI and limited-angle tomography in the sample’s frame of reference. Circled numbers denote the detector positions, and colors encode acquisition times (red/blue/green); the center depicts schematic melt-pool po