Microstructure Characterization and Mechanical Properties of Al6061 Alloy Fabricated by Laser Powder Bed Fusion

Processing high-performance aluminum alloys, including 6xxx and 7xxx series, via laser additive manufacturing (AM) processes poses significant challenges, primarily due to the rapid cooling rates inherent in these processes, which often result in solidification cracking and metallurgical defects. This study aimed at producing dense, crack-free samples of Al6061 alloys, using the laser powder bed fusion (L-PBF) process. Taguchi’s method of design of experiments was employed to study the effects of laser power, scanning speed, and hatch spacing on the L-PBF process parameters for Al6061. Two types of samples were fabricated: cubic samples for density and microstructural analyses; and dog bone samples for tensile testing. The microstructure, density, mechanical properties, fractography, and material composition of the L-PBF Al6061 parts were investigated. Based on our experimental findings, an optimal process window is suggested, with a laser power of 200–250 W, scanning speed of 1000 mm/s, and hatch spacing of 140 µm, resulting in complete melting within the energy density range of 44–50 J/mm3. This work demonstrates that adjusting processing conditions—specifically, increasing the energy density from 25.51 J/mm3 to 44.64 J/mm3—leads to a reduction in porosity from approximately 5% to below 1%, significantly improving the density and quality of the parts fabricated using L-PBF.