Ultrauniform, strong, and ductile 3D-printed titanium alloy through bifunctional alloy design

Coarse columnar grains and heterogeneously distributed phases commonly form in metallic alloys produced by three-dimensional (3D) printing and are often considered undesirable because they can impart nonuniform and inferior mechanical properties. We demonstrate a design strategy to unlock consistent and enhanced properties directly from 3D printing. Using Ti−5Al−5Mo−5V−3Cr as a model alloy, we show that adding molybdenum (Mo) nanoparticles promotes grain refinement during solidification and suppresses the formation of phase heterogeneities during solid-state thermal cycling. The microstructural change because of the bifunctional additive results in uniform mechanical properties and simultaneous enhancement of both strength and ductility. We demonstrate how this alloy can be modified by a single component to address unfavorable microstructures, providing a pathway to achieve desirable mechanical characteristics directly from 3D printing. Laser powder bed fusion provides the opportunity to make custom-built metal structures, but these objects can have undesirable variability in mechanical properties. Zhang et al. addressed the origin of this issue, unwanted metastable phases and columnar-shaped crystals, by adding molybdenum nanoparticles to a common aluminum alloy (see the Perspective by Zhang and Wang). The nanoparticles both encouraged the growth of symmetric grains and suppressed the formation of unwanted phases. The resulting samples made from laser powder bed fusion have much better mechanical properties, showing the promise of this design strategy. —Brent Grocholski Molybdenum nanoparticles enable uniform and enhanced mechanical properties of a titanium alloy produced by 3D printing.