Materials

For stronger 3D-printed titanium alloys – just add copper?

For stronger 3D-printed titani...
A pair of 3D-printed titanium-copper bars, alongside piles of titanium alloy and copper powder
A pair of 3D-printed titanium-copper bars, alongside piles of titanium alloy and copper powder
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A pair of 3D-printed titanium-copper bars, alongside piles of titanium alloy and copper powder
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A pair of 3D-printed titanium-copper bars, alongside piles of titanium alloy and copper powder
A 3D-printed titanium-copper block, made at RMIT
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A 3D-printed titanium-copper block, made at RMIT

The ability to 3D print titanium-alloy objects certainly does open up some intriguing possibilities. That said, the finished items aren't always as strong as they could be. Now, new research suggests that adding copper to those alloys could make a big difference.

Typically, when objects are being 3D printed out of titanium alloy, a laser is used to selectively melt a powder consisting of titanium particles and other chemical elements. In this fashion, items are built up a layer at a time, as each layer of melted powder cools into a solid.

According to scientists at Australia's RMIT University, however, problematic column-shaped crystals form within the material as it cools and bonds. These ultimately make the end product more prone to cracking and distortion.

And unfortunately – unlike the case with some other metals – there are no commercially-available grain-refining compounds that can be used with titanium alloys, in order to address the problem.

Working with colleagues from CSIRO (the Commonwealth Scientific and Industrial Research Organisation), the University of Queensland and the Ohio State University, RMIT researchers instead looked to copper. More specifically, they experimented with 3D printing objects out of a titanium alloy powder that was mixed with copper powder. The resulting solid material showed great promise.

A 3D-printed titanium-copper block, made at RMIT
A 3D-printed titanium-copper block, made at RMIT

"Of particular note was its fully equiaxed grain structure: this means the crystal grains had grown equally in all directions to form a strong bond, instead of in columns, which can lead to weak points liable to cracking," says RMIT's Prof. Mark Easton. "Alloys with this microstructure can withstand much higher forces and will be much less likely to have defects, such as cracking or distortion, during manufacture."

It is hoped that once the technology is developed further, such titanium-copper alloys could find use in fields such as medicine, defence and aerospace.

A paper on the study was recently published in the journal Nature.

Source: RMIT

5 comments
Wombat56
That's nice, but what percentage of each metal is used and what effect does it have on the characteristics of the end product i.e melting point, tensile strength etc?
Kpar
Good questions, Wombat56, especially about tensile strength and melting point. I am not surprised, however, that they left out details of the mixture. Proprietary interests, of course.
Expanded Viewpoint
Recently on this site, there was an article about how adding a small percentage of gold to an alloy greatly increased its hardness. Who knows what other elements might be used to obtain better alloys? Just a little bit of carbon and other elements added to iron change its properties radically! With additive manufacturing, you don't have to worry so much about separation of the elements or boil off due to higher melting points. And doing the process in an inert gas or vacuum environment opens up even more possibilities as well. One might also use a hyperbaric chamber with various gaseous elements in it.
Eric Blenheim
The alloy four times harder than titanium that is produced by mixing it with gold is so hard that it does not wear down to produce toxic nanoparticles of titanium that otherwise result from degradation of some other softer titanium alloy type hip joints by abrasion. I wonder if that alloy with gold could be 3D- printed for hip joints and knee joints without losing strength? The easiest solution for such medical purposes would appear to be first making a perfect cast from MRI scans through 3D printing to pour the molten metal titanium gold alloy mix into and do it that way.
Trylon
I'm waiting for the article that says graphene can help the strength of 3D printed titanium alloys. Why not? Seems they find another use for that miracle material every few days.