Solid-state cold spray additive manufacturing of pure tantalum with extraordinary high-temperature mechanical properties

Solid-state cold spray additive manufacturing (CSAM) was used to fabricate pure tantalum (Ta) and the high-temperature mechanical and deformation behavior of this material was investigated. The pure Ta fabricated using CSAM consists of irregularly shaped powder particles elongated in the direction perpendicular to the spraying direction. In addition, microstructural evolution occurs in the process of accommodating harsher plastic deformation along the boundaries between powder particles. Compression test results confirmed that the room temperature yield strength was approximately 901 MPa, which is four to six times higher than that of pure Ta produced using conventional processes such as vacuum arc melting etc. Moreover, CSAM Ta has excellent mechanical properties even at high temperatures, and these properties were confirmed to be retained up to approximately 950 °C. Surface and microstructural observations after deformation revealed that the sample crumbled in a compression test at 800 °C. However, the sample retained its shape at temperatures above 800 °C. This phenomenon was a result of the interaction between high-temperature oxidation behavior and microstructural evolution, i.e. dynamic recrystallization. Based on these findings, the relationship among the microstructure, room-to high-temperature mechanical properties, and deformation behaviors are also discussed.