Advancing multi-material laser powder bed fusion through topology optimized design

Recent advancements in Multi-Material Laser Powder Bed Fusion (MM-LPBF) offer the unique ability to additively manufacture highly complex structures by selectively depositing multiple material systems within a single layer in the conventional laser powder bed process. MM-LPBF combines the fine resolution of typical LPBF processes with the ability for high resolution spatial control of multiple material placements. The alternating active phase (AAP) algorithm is applied to design a multi-material Messerschmitt-Bölkow-Blohm (MBB) beam, minimizing compliance while also considering manufacturability. Topologically optimized solutions were fabricated through MM-LPBF (316 L stainless steel and CuCrZr) and evaluated through flexural testing with digital image correlation (DIC) and mechanical performance was compared to finite element analysis (FEA). Microstructure characterization of the bi-material interface revealed localized MM-LPBF process-specific defect formation. Mechanical testing revealed progressive stages of failure initiating in the bulk CuCrZr regions and propagating to interfacial regions. DIC analysis indicated that stiffness of the multi-metal MBB structure was within 5.3% of the predicted stiffness from FEA. Findings from this study demonstrate that highly complex multi-material topologically optimized (MM-TO) designs, which were otherwise not plausible to manufacture through either traditional or AM methods, are now feasible at high resolution. The applied method can be extended to other applications which would benefit from multi-objective criterion such as multi-material heat exchangers, biomedical devices, and energy storage devices. Finally, this research highlights the need for further MM-LPBF process development to reduce bulk porosity and interfacial defects, as its processing physics differ significantly from single material LPBF and other metal AM processes.