Dual-laser powder bed fusion additive manufacturing: computational study of the effect of process strategies on thermal and residual stress formations

A multi-laser powder bed fusion additive manufacturing can shorten manufacturing time and enable greater possibilities of process optimization. Nonetheless, previous studies showed that the process-dependent characteristics from the single laser may not fully translate to the multi-laser system. Therefore, the present work utilized a three-dimensional thermomechanical model to study the influence of process conditions on the physical behaviors of the dual-laser system of Ti-6Al-4V. Numerical results revealed that the dual-laser process could reduce the cooling rate and residual stress by approximately 70 and 30%, respectively. In addition, statistical analysis was employed to determine the level of influence and the contribution of each process parameter. Cooling rates and stress magnitudes were mainly controlled by the secondary laser power, and the scan length of the primary laser largely dictated the stress anisotropy. Therefore, although the dual-laser system can provide in-situ residual stress reduction, the understanding of process-controlled thermal and mechanical characteristics was proven essential to achieve desirable responses.