Microstructural Evolution of Ti-2.5Cu Alloys Produced by Powder Metallurgy and Laser Powder Bed Fusion

The present research is a comparative study of microstructure evolution and mechanical properties between Ti-2.5Cu alloys processed via powder metallurgy (P/M) and laser powder bed fusion (LPBF) using non-spherical Cu powders. P/M specimens were cold pressed and sintered at three different temperatures, 1000 degrees C, 1100 degrees C, and 1200 degrees C. LPBF specimens were prepared with two scanning speeds and three laser powers to achieve different volumetric energy density (VED) levels. An optimum VED in the range between 60 and 75 J/mm3 resulted in low porosity (0.5 to 6 pct) compared to P/M samples (10 to 25 pct). Both processing routes led to microstructural heterogeneities. In the LPBF specimens, the heterogeneities were induced by the lower laser absorption and high reflectivity of elemental Cu and process parameters of scanning speed and laser power, whereas in the P/M route, they occurred due to the formation of liquid phase during sintering. These heterogeneous microstructures resulted in a hardness 23 pct higher for the sintered condition in comparison to LPBF. Moreover, the porosity and the VED directly affected the hardness of the P/M and LPBF methods, respectively.