The laser–matter interaction and solidification phenomena associated with laser additive manufacturing (LAM) remain unclear, slowing its process development and optimisation. Here, through in situ and operando high-speed synchrotron X-ray imaging, we reveal the underlying physical phenomena during the deposition of the first and second layer melt tracks. We show that the laser-induced gas/vapour jet promotes the formation of melt tracks and denuded zones via spattering (at a velocity of 1 m s−1). We also uncover mechanisms of pore migration by Marangoni-driven flow (recirculating at a velocity of 0.4 m s−1), pore dissolution and dispersion by laser re-melting. We develop a mechanism map for predicting the evolution of melt features, changes in melt track morphology from a continuous hemi-cylindrical track to disconnected beads with decreasing linear energy density and improved molten pool wetting with increasing laser power. Our results clarify aspects of the physics behind LAM, which are critical for its development.
展开▼
机译：与激光增材制造（LAM）相关的激光物质相互作用和凝固现象仍然不清楚，从而减慢了其工艺开发和优化的进程。在这里，通过原位和操作高速同步加速器X射线成像，我们揭示了第一层和第二层熔体轨道沉积过程中的潜在物理现象。我们表明，激光诱导的气体/蒸气射流通过飞溅（速度为1 m s -1 ）促进熔体轨迹和裸露区域的形成。我们还揭示了由Marangoni驱动的流动（以0.4μms -1 的速度再循环）引起的孔迁移，激光重熔引起的孔溶解和分散的机制。我们开发了一种机制图，用于预测熔体特征的演变，熔体轨道形态的变化（从连续的半圆柱形轨道到断开的珠子），其线性能量密度降低，熔池润湿性随着激光功率的增加而改善。我们的结果阐明了LAM背后的物理学方面，这对它的发展至关重要。
展开▼
