Different types of metal have different qualities, so combining them can result in items that outperform those made of any one metal. A new technique now allows such mixing to be performed by 3D printers, faster and easier than ever before.
Currently, one of the most common methods of 3D printing objects out of multiple metals incorporates a technique known as wire arc additive manufacturing.
In a nutshell, this involves utilizing a weld head to produce an electrical arc that melts a metal wire. That molten metal is deposited in successive layers, incrementally building up the desired item. And every time that a different metal is required within one print job, the process has to be paused so that a wire made of one metal can be swapped out for one made of another.
Seeking to streamline that process, a Washington State University team led by Prof. Amit Bandyopadhyay developed a new technique which incorporates two commercially available weld heads, each one loaded with a wire made of a different metal.
One head initially deposits one metal in a circular pattern, forming a ring. The other head then rushes in and deposits the other type of metal inside that ring, giving the structure a solid core. As the two metals proceed to cool, the outer ring shrinks at a faster rate than the inner core. This produces pressure at the interface between the two metals, binding them together.
The process is repeated over and over, layer by layer, ultimately resulting in a single "bimetallic" column.
So far the scientists have created bimetallic structures – such as a column with a stainless steel core contained within a milder steel casing – which were 33% to 42% stronger than equivalent structures made of either metal on its own.
It is hoped that the technique could ultimately be used to create products such as torque-resistant axle shafts, spacecraft parts with cooling cores surrounded by heat-resistant casings, or even artificial hip implants with a therapeutic magnetic core encased in durable titanium.
And the items wouldn't necessarily have to take the form of rods or columns.
"The example we have shown in this work is radial structures, where the two materials are placed radially," Bandyopadhyay told us. "[But] we should be able to make any design that can be 3D printed."
A paper on the research was recently published in the journal Nature Communications. The bimetallic printing process is demonstrated in the following video.
Source: Washington State University
