Schlieren and X-ray imaging of laser-particle interactions in metal additive manufacturing

In laser powder bed fusion (LPBF), the most widely adopted additive manufacturing (AM) technique for metallic parts, the multiphase flow dynamics of the laser-material interactions strongly influence the quality of printed parts. Coaxial, high-speed synchrotron X-ray combined with schlieren imaging can therefore give deeper insight into the physics of such flows, by enabling simultaneous visualisation of all phases of matter present. In this work, atmospheric fluid and particle dynamics of Ti-6Al-4V are characterised under varying laser energy input, which can drastically change the morphology and stability of the liquid-vapour interface, as well as the intensity of the vapour jet. Characteristic laser-particle interactions that can affect mass transfer and defect formation are showcased. Data fusion and image analysis aid in relating our observations to process stability and optimisation.