Cellular structures boost 3D printed metal strength
Researchers from the University of Osaka isolate the strengthening role of nano-scale cellular structures in metal AM
A research group from the University of Osaka has conducted quantitative individual analysis on the contribution to the strength of the micrometer-scale crystallographic lamellar structures and nanometer-sized cellular structures that are formed spontaneously, hierarchically, and specifically by metal 3D printing technology, and revealed that the cellular structure (cell-specific interfaces) is a factor that brings about extremely significant strengthening. Their paper, “Remarkable Strengthening Effects of Cells in Laser Powder Bed Fusion-Processed Inconel 718,” was published in Materials Research Letters.
In order to clarify the contributions individually, the research group, including Taichi Kikukawa (Master’s Course), Specially Appointed Professor Takuya Ishimoto, and Professor Takayoshi Nakano of the Graduate School of Engineering at the University of Osaka, established a method to independently eliminate the cellular structure by heat treatment and the lamellar structure by designing a unique scanning strategy.
As a result, while the presence of the lamellar structure increased the strength by a few percent, the cellular structure increased the strength by 40%, revealing the extremely high strengthening effect of the cellular structure.
The strengthening effect of the cellular structure discovered in this study, combined with the strengthening mechanism and strength anisotropy that have been clarified so far in 3D printing materials, as well as the shape-based functionality that 3D printing excels at, is expected to break through the limitations of conventional mechanical functions and greatly expand the scope of artificially customized mechanical function control.
It has been reported that various alloys created by the LPBF method have higher strength than alloys created by conventional methods such as casting, and there is growing interest worldwide in their material properties. Against this background, there is a demand to clarify and control the properties and characteristics of strengthening factors to increase the strength of alloys, and the flexible designing of strength.
However, since multiple unique structures coexist at various scales inside objects created by metal 3D printing, it is difficult to isolate the strengthening caused by each unique structure, and quantitative identification of strengthening factors has not been realized.
The knowledge gained in this study on strengthening by cellular structures means that replacing traditionally-made parts with those produced using LPBF has the potential to bring about not only a change in manufacturing method, but also a dramatic improvement in the mechanical function of the product and its ultra-lightweighting.
Cellular structures appear in many alloy systems during the LPBF process based on the concentration distribution during solidification. In other words, since this result can be applied to various alloy materials that make up social infrastructure products, the researchers expect the ripple effects of this result to extend to an extremely wide range of industrial fields.
