Titanium (Ti) can be found everywhere, from tennis rackets to jet engines. Titanium alloys offer high tensile strength, light weight, and extraordinary corrosion and extreme temperature tolerance, making them valuable materials in the construction of planes, armor plating, naval ships, and spacecraft. Welded titanium pipe is used in the chemical and petroleum drilling industries for its corrosion resistance. For more information about titanium and its many uses, read Titanium: This Lightweight Does Some Heavy Lifting in the Metals Industry or take a look at this infographic to learn 9 Fast Facts About Titanium.
The rise of additive manufacturing, or 3D printing as it’s commonly known, is only increasing the use of this versatile metal. 3D printing with metal was once cost-prohibitive, but now 3D printing technologies for metal may be more efficient than some traditional manufacturing methods and produce a comparable, or even better product, depending on the application. Direct metal laser sintering (DMLS) for example, is able to quickly create very complex geometries and is being applied to the manufacture of jet engine parts that can be difficult to produce using conventional methods. The DMLS technique is also able to handle a wider range of alloys to create stronger, more durable parts.
Metal 3D printing is advancing because the materials used in the process are also evolving. Metal powders tailored to specific 3D printing technologies are emerging rapidly to meet the many applications in the aerospace, automotive and other industries. Formulations include various grades of stainless steel, low alloy steels, nickel and cobalt alloys, titanium alloys, or other metal alloys.
3D-printed metal alloys offer the advantages of design flexibility with less material waste and cost. In the case of titanium, however, powder-based printing methods also increase the quantity and size of pores in the final product, which can decrease the material’s resistance to fatigue or cyclic strain and lead to breakage, as explained in an article on the Argonne National Laboratory website. To understand the cause of porosity in 3D-printed titanium alloys, researchers from Carnegie Mellon University and the Argonne National Laboratory inspected a common titanium alloy, Ti-6Al-4V, at the micron-scale using microtomography, a rapid imaging tool. Additively manufactured Ti-6Al-4V includes 6% aluminum and 4% vanadium and is popular in the aerospace and biomedical industries where speed of manufacture and unique designs are important.
The study focuses on Ti-6Al-4V powders printed by electron-beam melting (EBM). As the titanium powder heats, gases trapped in the material can create pores that range from a few microns to a few hundred microns in size and are unevenly distributed throughout the material.
The researchers quantified the number, volume and distribution of pores in samples of Ti-6Al-4V using a range of printing parameters that did significantly impact porosity, but did not eliminate it. Printing larger melt pool areas at lower speed resulted in fewer, smaller pores overall, but those samples also showed clustering of pores at the surface, leading the researchers to focus on the titanium alloy powder rather than printing parameters.
Metal alloy composition, whether it’s being used in an additive or traditional manufacturing application, must be verified to ensure product chemistry specifications are met. Wavelength-dispersive x-ray fluorescence (WDXRF) is a nondestructive analytical method that quickly provides the exact percentages of a wide range of elements for material characterization and analysis.
Recommended reading: Welcome the Next Phase in the 3D Printing Craze: Metal.