Eliminating defects and improving microstructure and mechanical properties of additively manufactured TiAl alloy via spark plasma sintering post-treatment

• A new strategy to eliminate defects in LPBFed parts via SPS post-treatment was proposed. • Eliminating defects while inhibiting grain coarsening in LPBFed TiAl was realized. • Crack-free Ti-48Al-2Cr-8Nb with porosity of 0.04% was obtained after SPS treatment at 1150 ℃. • The tensile strength of LPBFed TiAl can be greatly enhanced via SPS treatment. • The phase transform mechanism of the as-LPBFed TiAl sample after SPS treatment was revealed. Laser powder bed fusion (LPBF) additively manufactured components exhibit numerous defects that negatively impact their mechanical properties and reliability. For instance, TiAl intermetallic alloys in LPBF process are prone to generate numerous cracks and pores, which significantly reduce their tensile strength and severely limit their applications. This study introduces a novel approach utilizing spark plasma sintering (SPS) as a post-treatment method to effectively eliminate these defects while maintaining the refined microstructures in LPBF-fabricated TiAl (Ti-48Al-2Cr-8Nb) alloy. Through SPS post-treatment, crack-free TiAl samples with a porosity as low as 0.04 % and an average grain size of approximately 2 μm are obtained. The tensile strength of the treated sample is significantly increased to 353.2 MPa, marking the highest reported value to date. This improvement is attributed to the high degree of densification and the effective elimination of cracks and pores. Additionally, the structural evolution and underlying mechanisms of LPBF-built TiAl alloys during SPS treatment have been thoroughly examined. The proposed strategy, which simultaneously addresses defect reduction and refined microstructure preservation through SPS post-treatment, demonstrates potential for broad application across various materials and additive manufacturing processes. It is anticipated to develop into a universally applicable post-treatment method for components produced via additive manufacturing.