X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA.
Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Sci Rep. 2017 Jun 15;7(1):3602. doi: 10.1038/s41598-017-03761-2.
We employ the high-speed synchrotron hard X-ray imaging and diffraction techniques to monitor the laser powder bed fusion (LPBF) process of Ti-6Al-4V in situ and in real time. We demonstrate that many scientifically and technologically significant phenomena in LPBF, including melt pool dynamics, powder ejection, rapid solidification, and phase transformation, can be probed with unprecedented spatial and temporal resolutions. In particular, the keyhole pore formation is experimentally revealed with high spatial and temporal resolutions. The solidification rate is quantitatively measured, and the slowly decrease in solidification rate during the relatively steady state could be a manifestation of the recalescence phenomenon. The high-speed diffraction enables a reasonable estimation of the cooling rate and phase transformation rate, and the diffusionless transformation from β to α phase is evident. The data present here will facilitate the understanding of dynamics and kinetics in metal LPBF process, and the experiment platform established will undoubtedly become a new paradigm for future research and development of metal additive manufacturing.
我们采用高速同步加速器硬 X 射线成像和衍射技术，原位实时监测 Ti-6Al-4V 的激光粉末床熔合（LPBF）过程。我们证明，LPBF 中的许多具有科学和技术意义的现象，包括熔池动力学、粉末喷出、快速凝固和相变等，可以以前所未有的空间和时间分辨率进行探测。特别是，用高空间和时间分辨率实验揭示了关键孔的形成。测量了凝固速率，在相对稳定状态下凝固速率的缓慢下降可能是回热现象的表现。高速衍射能够合理估计冷却速率和相变速率，从β到α相的无扩散转变是显而易见的。这里呈现的数据将有助于理解金属 LPBF 过程中的动力学和动力学，所建立的实验平台无疑将成为未来金属增材制造研究和发展的新模式。
