Real-time monitoring of laser powder bed fusion process using high-speed X-ray imaging and diffraction

TLDR

High‑speed synchrotron hard X‑ray imaging and diffraction were used to monitor Ti‑6Al‑4V laser powder bed fusion in situ and in real time. The study revealed keyhole pore formation, quantified solidification and cooling rates, observed a diffusionless β→α′ phase transformation, and demonstrated that high‑resolution X‑ray imaging and diffraction can probe melt‑pool dynamics, powder ejection, rapid solidification, and phase changes, providing a new platform for understanding metal LPBF kinetics.

Abstract

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.