ORNL team combines 3D printing and casting to make stronger aluminium/steel composite parts

3D printing has revolutionised the metal manufacturing sector including aluminium. Recently, material scientists from the Oak Ridge National Laboratory (ORNL) and Rice University in Houston, Texas have developed a new process for creating “damage-tolerant components” made from multiple materials by combining both 3D printing with traditional casting methods.

The innovative project titled “Damage-tolerant metallic composites via melt infiltration of additively manufactured preforms,” shows how a fusion of 3D printing with casting process  can result in optimized parts which are stronger than purely 3D printed or casted parts. According to the researchers the new two-step process eliminates “issues with intermetallic formation, cracking, and poor resolution” that are common in most 3D printing processes.

Model of a 3D printed preform structure

The ORNL researchers first produce a lattice preform structure using selective laser melting (SLM) technology. This functions as a sort of skeleton for the final component. Then they infiltrate the preform with a “liquid metal that had a melting temperature lower than that of the reinforcement.”

As an experiment, the researchers poured an aluminium alloy (A356) over a 3D printed lattice made from 316L grade steel. The produced part, an “interpenetrating phase composite” (or IPC), was proven to have higher damage tolerance than a part made purely from aluminium alloy.

The compression tests and tension tests conducted on the 3D printed composite part showed much improvement when compared with parts made from aluminium alloy on its own.

“Inspection of the as-tested tensile specimens suggested that this exceptional damage tolerance is a result of the interpenetrating structure of the constituents,” reads the paper’s abstract.

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“The key advantage of this processing strategy over other fusion-based metal additive manufacturing techniques is that in this two-step process, liquid-phase mixing of the constituents is excluded. As a result, we are able to overcome problems with cracking and poor resolution that limit most of the other fusion-based additive manufacturing techniques for printing composites,” adds the report.

According to the research team, this hybrid manufacturing process could be successfully applied in the automotive industry, which requires parts with optimal thermal and mechanical properties. The composite parts manufactured using the 3D printing-casting process could meet these required benchmarks.