AA6061 is prone to porosity and solidificationSolidification cracking under rapid solidificationRapid solidification conditions, presenting significant processingProcessing challenges in additive manufacturingAdditive manufacturing. In this study, process parametersProcess parameter of modulated, specifically frequency and duty cycle, in the laser powder bed fusionLaser Powder Bed Fusion (LPBF) process, have been systematically investigated to examine the microstructureMicrostructure and defects of AA6061, including grains, subgrains, porosity, and cracking. High frequency with a low duty cycle led to multiple melt pool boundaries within a single melt track, refined grains and subgrains, and reduced cracks. In contrast, high frequency with a high duty cycle resulted in a continuous melt track with coarse grains due to sustained meltingMelting. This processingProcessing condition also reduced porosity and cracks compared to low duty cycle laser modulationsLaser modulation. Microhardness was conducted to assess the mechanical propertiesMechanical properties. These findings signify that the application of modulated laser processingProcessing is an effective strategy for controlling microstructureMicrostructure and minimizing defects in additively manufactured aluminum alloysAluminum alloy.