Strength–ductility synergy strategy of Ti6Al4V alloy fabricated by metal injection molding

Abstract

Interstitial oxygen (O) contamination remains a substantial challenge for metal injection molding (MIM) of titanium alloys. Herein, this critical problem is successfully addressed by regulating the thermal debinding temperature and incorporating the oxygen scavenger LaB₆. Results indicate that the surface oxide layer (with a thickness of (13.4 ± 0.5) nm) of Ti6Al4V powder begins to dissolve into the Ti matrix within the temperature range of 663–775°C. O contamination in MIM Ti alloys can be effectively mitigated by lowering the thermal debinding temperature and adding LaB₆ powder. As a result of reduced dissolved O content, the slips of mixed <a> and <c + a> dislocations are effectively accelerated, leading to improved ductility. Moreover, grain refinement, along with the in situ formation of TiB whiskers and second-phase La₂O₃ particles, enhances the strength of the material. The fabricated MIM Ti6Al4V sample exhibits excellent mechanical properties, achieving an ultimate tensile strength of (967 ± 5) MPa, a yield strength of (866 ± 8) MPa, and an elongation of 21.4% ± 0.7%. These tensile properties represent some of the best results reported in the literature for MIM Ti6Al4V alloys. This study offers valuable insights into the development of high-performance MIM Ti alloys and other metal materials.

Keywords

titanium / metal injection molding / oxygen / LaB₆ / mechanical properties

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University of Science and Technology Beijing