Due to its excellent physical properties and resistance to infection, titanium alloy is the primary choice for the manufacture of orthopedic devices such as knee/hip implants. So far, researchers have used selective laser melting (SLM) techniques and titanium-aluminum powders to 3D print biological prototypes. SLM technology typically USES high power lasers to build 3D objects layer by layer from computer design models. But aluminium has a long history of adverse effects on the nerves, leading scientists to hope to find other materials to replace it.
In theory, titanium and tantalum alloys are perfectly fine, because they are both biocompatible and their mechanical properties are due to pure titanium. But tantalum has a very high melting point (more than 3,000 degrees Celsius), which means that turning titanium into a spherical metal powder that can be used in SLM technology is not economically feasible. Tantalum powder commonly used in the market is usually formed by gas atomization of long coarse particles.
To overcome this problem, the team mixed the coarse tantalum powder with another commercially available microspherical titanium powder. After mixing the two materials for half a day, they observed that the mixture could be laid more evenly, making SLM technology easier to use. Microscopic experiments have revealed that the spherical shape of titanium remains after mixing, which is key to the mixture's successful use in 3D printing.
By alternating molten metal up and down in a checkerboard pattern of laser scanning or moving from side to side to reduce thermal stress, the researchers successfully used SLM technology to create the 3-d shape of ti-ta alloy. Surprisingly, X-ray and other imaging techniques have shown that the addition of tantalum, combined with rapid solidification, promotes and stabilizes the formation of high strength layered titanium grains.
