Additive technologies are penetrating many new areas and promise to significantly change the very essence of production over time. Printing saves materials and flexibly adapts to new products, which is especially important in the manufacture of large models, in particular car body parts. To do this, it is important to preserve the strength characteristics of the parts, which Japanese researchers have successfully accomplished.
Artistic representation of the process. Image source: Tohoku University
Scientists from Tohoku University investigated the effect of laser deposition 3D printing (L-PBF) modes on the strength of aluminum and steel alloy parts. This makes it possible to create lightweight and especially strong parts of car bodies, for example, shock absorber suspension struts. However, when alloy powder is melted by a laser during the manufacturing process of parts, brittle transition zones appear at the boundaries of two metals that do not meet technical requirements.
«Multimaterials are a hot topic in additive manufacturing due to the flexibility of the process, explains assistant professor Kenta Yamanaka. “However, the main problem in practical implementation is that for certain combinations of metals, such as steel and aluminum, brittle intermetallic compounds can form at the interfaces of dissimilar metals. So although the material is now lighter, it ends up being more brittle.”
Printed suspension element
The researchers found out what laser speed conditions should be observed to minimize the formation of intermetallic compounds. To do this, the car’s shock absorber mounts were printed at different laser speeds, and the crystal structure of the material at the interface was carefully studied.
Graph of loads withstood by samples depending on speed during printing
The scientists found that increasing the laser speed significantly suppressed the formation of brittle intermetallic compounds (such as Al₅Fe₂ and Al₁₃Fe₄). They hypothesized that higher sintering rates cause what is known as disequilibrium solidification, which minimizes the separation of solutes that leads to the formation of weak points in the material. The sample created by the researchers thus demonstrated exceptionally strong bonding surfaces.