Operando X-ray Diffraction During Laser 3D Printing of Multi-phases Alloys

Ming Chen¹, Samy Hocine¹, Steven Van Petegem¹, Helena Van Swygenhoven¹

¹Photons for Engineering and Manufacturing, Paul Scherrer Institute,

²Forschungsstrasse 111, 5232 Villigen PSI, Switzerland

ABSTRACT: Laser based additive manufacturing allows to build a designed shape layer by-layer, offering flexibility and versatility to fabrication metals with complex shapes. However, the fast cooling rates and repeated heat cycles depending on the laser and scanning parameters are difficult to measure with conventional methods. A recently developed operando X-ray diffraction device implemented at a synchrotron beamline, taking advantage of the high brilliance and the fast detectors available, bridges this gap with numerical methods shown in Figure 1. This miniaturized device allows to conduct laser powder bed fusion (L-PBF) process in a small chamber. Here, we show a case study on additive manufactory of Ti- 6Al-4V during L-PBF process by performing operando experiments. The temporal evolution of the low and high temperature phases are studied by controlling printing parameters to achieve different heating and cooling rates. The formation of residual stresses in the β phase is demonstrated. It is shown that the process parameter having the largest influence on the evolving microstructure in Ti-6Al-4V is the scanning strategy, such as scanning length. This study enables to optimize the microstructure of various multi-phase alloys by understanding details of the sequence of phase transitions and microstructure evolution during dynamic process of additive manufactory. 

Figure 1.Diffraction geometry during an operando experient.