Controlling interdependent meso nanosecond dynamics and defect generation in metal 3D printing
Circumventing spatter Laser powder bed fusion is an additive manufacturing technique that laser melts powder layer by layer to build a three dimensional (3D) part. Khairallah et al. used experiments and a multiphysics model to determine the origin of the melt spatter and defect formation that degrade the properties of built parts (see the Perspective by Polonsky and Pollock) Informed modulation of laser power is important to avoid disturbing the powder bed and creating laser shadowing. This reduces pore formations and leads to more uniform properties of 3D printed parts. Science, this issue p. 660; see also p. 583 Multiscale physics models help isolate a stability criterion that is useful for avoiding defects in laser bed powder fusion printing. State of the art metal 3D printers promise to revolutionize manufacturing, yet they have not reached optimal operational reliability. The challenge is to control complex laser powder melt pool interdependency (dependent upon each other) dynamics. We used high fidelity simulations, coupled with synchrotron experiments, to capture fast multitransient dynamics at the meso nanosecond scale and discovered new spatter induced defect formation mechanisms that depend on the scan strategy and a competition between laser shadowing and expulsion. We derived criteria to stabilize the melt pool dynamics and minimize defects. This will help improve build reliability.
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