Laser metal additive manufacturing (AM) requires precise coupling of energy to produce desired mechanical and morphological properties of printed structures. Large thermal gradients, complex melt pool instabilities and poor absorptivity are application-limiting detriments in laser powder bed fusion-enabled metal AM, ultimately resulting in poor mechanical properties. Current approaches to improving the mechanical robustness of structures printed using metal additive manufacturing (AM) come at the expense of print reliability, consistency cost and integrability. However, Gaussian-like process laser beams commonly employed in metal AM limit control over thermomechanical processes that govern microstructural and macroscale properties. Here, we employ laser beams shaped in amplitude and polarization, to deliver controlled optothermal profiles on the powder bed. Highspeed imaging and other in situ diagnostics are employed to gain a deeper understanding of the process physics at the melt pool. We also implement ultrashort pulses as a secondary beam source, to control microstructure and surface quality by tuning the cooling rates. Unique optical properties of such single and dual-beam approaches result in reduced defects and controlled grain texture across a broad process parameter window. We will report on these experiments, coupled with in-line diagnostics, during printing of Ti-6Al-4V and SS 316L alloys.


Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-862892