Caltech redefines metallurgy with 3D printing breakthrough
The technique identifies optimal metal combinations for desired outcomes, even enabling the creation of unexpectedly strong copper–nickel alloys
According to Caltech, scientists have developed a new method for creating metallic objects with precisely defined shapes and compositions, offering unprecedented control over alloys and their properties. This advancement could enable the production of “biocompatible and mechanically robust” stents or “strong but lightweight” satellite parts tailored for longevity in space. The technique identifies optimal metal combinations for desired outcomes, even enabling the creation of unexpectedly strong copper–nickel alloys.
“If you look at how metallurgy has been done for centuries,” says Professor Julia R. Greer, “you nearly always start with a raw ore… and basically, the mechanical properties… are limited.” This new method, she explains, allows fine-tuning of both chemical composition and microstructure to significantly enhance mechanical resilience.
The method, described in Small, was developed by Thomas T. Tran (PhD ’25), with Rebecca Gallivan (PhD ’23) as second author. It builds on earlier work from Greer’s lab using hydrogel-infusion additive manufacturing (HIAM), a type of 3D printing. Previously, HIAM could only print with one metal. Tran expanded it to print copper–nickel alloys with variable compositions, which significantly influence the resulting material’s properties.
The process begins by 3D printing a hydrogel scaffold layer by layer. This scaffold is soaked in a solution of metallic salts. After calcination—burning away the organic matter—metal oxides remain. These are then subjected to reductive annealing: heating in a hydrogen-rich environment, which removes oxygen and leaves behind a metallic alloy.
“The composition can be varied in whatever manner you like, which has not been possible in traditional metallurgy processes,” says Greer. “One of our colleagues described this work as bringing metallurgy into the 21st century.”
By analyzing the alloys’ microstructure and performing mechanical testing, the researchers found that HIAM alloys form more homogeneously than those made by other methods. Using a transmission electron microscope, they observed highly symmetrical crystal structures influenced by metal–oxide transitions during annealing.
Surprisingly, the strength of these alloys depends not only on grain size but also on composition. A Cu12Ni88 alloy is nearly four times as strong as a Cu59Ni41 one. The presence of nanoscale metal–oxide interfaces from the HIAM process further strengthens the material.
The research was supported by the US Department of Energy and the National Science Foundation.
