Rapid X-ray microscopy and XRD of the 3D metal printing process
The aim of this project is to capture dynamics during the melt, flow, and re-solidification of a metal powder bed during selective laser melting in real time using in situ, rapid X-ray microscopy and XRD. The high flux and penetrating power of the hard X-ray, synchrotron sources enables up to 40 kHz imaging with 2 micron imaging resolution with white light and X-ray diffraction up to 2 kHz in a 50 micron field of view with 20 keV x-rays. With these two techniques we can study the rapid liquid-solid dynamics through the depth of the powder bed. Other in situ characterization techniques are only sensitive to the surface. With X-ray imaging we have studied the dynamics of the vapor depression in the keyholing regime and how these lead to pore formation. With X-ray diffraction we have quatified the cooling rate of the solid phase after melt and resolidification.