When you think of titanium, you might think of its widespread applications in aerospace and medical implants – after all, this metal boasts an exceptionally high strength-to-weight ratio, excellent corrosion resistance, and biocompatibility, making it a true "jack-of-all-trades" in the world of metals. However, for a long time, titanium has faced a "happy problem": pure titanium's absolute strength is too low to meet high-strength requirements; while alloying it with elements like Al and V improves its strength, it also degrades its corrosion resistance and biocompatibility, and presents challenges in recycling the alloying elements and potential resource depletion.
Recently, a study published in *Materials Research Letters* has offered new hope for solving this challenge. A research team from the Technical University of Denmark and the Suzhou Laboratory successfully fabricated a "sandwich-like" heterogeneous layered pure titanium plate through an innovative combination of laser powder bed fusion (LPBF) additive manufacturing technology and traditional manufacturing. This titanium plate not only achieved a yield strength of 439 MPa and a tensile strength of 596 MPa, but also possessed an exceptionally high uniform elongation of 27%, breaking the traditional understanding that titanium materials cannot simultaneously possess both high strength and ductility.
Core Innovation: How is the "sandwich" structure achieved using LPBF technology? To understand the performance breakthrough of this titanium plate, one must first understand its "special structure." The research team adopted a composite approach of "traditional substrate + additively manufactured layer," with the specific steps being a testament to "precision engineering":
1. "Careful Selection" of Raw Materials: Substrate: A traditionally manufactured Gr2 pure titanium plate was selected, with a thickness of 2mm and an internal structure of equiaxed grains with an average diameter of 22.4μm – this structure gives the substrate good ductility but low strength. Printing powder: Also Gr2 pure titanium powder, with a particle size controlled between 5~40μm and an average particle size of 25.8μm, prepared by gas atomization to ensure the uniformity and flowability of the powder.
2. The research team using the LPBF (Laser Powder Bed Fusion) "layer-by-layer stacking" technique did not directly print a complete titanium plate. Instead, they used a traditional substrate as an "intermediate layer," printing 25 layers of titanium material on each side of the substrate using LPBF technology (each layer 40μm thick, with a total printed thickness of approximately 1mm). During the printing process, the laser power was set to 280W, the scanning speed to 1200mm/s, and a "staggered checkerboard path" was specifically used, with the scanning direction rotated by 67° for each layer-the precise control of these parameters laid the foundation for the subsequent gradient microstructure. The resulting titanium plate resembles a "metal sandwich": a soft traditional titanium substrate in the middle, with hard additively manufactured layers on both sides, and no obvious gaps between the substrate and the printed layers-because during the printing of the first layer, the substrate surface is melted by the laser, forming a "metallurgical bond," completely avoiding the weak interface problem of traditional layered materials. The performance miracle: the "microscopic code" behind the 27% uniform elongation. Why can this "sandwich" structure allow the titanium plate to possess both high strength and high ductility? The answer lies in its microstructure and deformation mechanism.
In conclusion, from the dilemma of "strength and ductility being mutually exclusive" to the breakthrough of achieving "27% uniform elongation + 596 MPa tensile strength," this research, through the ingenious design of a "sandwich" structure and the precision of LPBF technology, has opened a new window for the development of titanium materials. Perhaps in the near future, we will see this novel "soft and hard" titanium material being used in more high-end equipment.
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