Tailoring microstructure and mechanical properties of β-solidifying TiAl alloy fabricated by laser-engineered net shaping through heat treatment

• Published in: Additive manufacturing Vol. 67; p. 103502
• Main Authors: Huang, Danni, Yao, Xiyu, Zhou, Yinghao, Zhu, Qiang, Tang, Yaxin, Huang, Han, Zhang, Ming-Xing, Yan, Ming
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.04.2023
• Subjects: Additive manufacturing; Creep; Heat treatment; Microstructure; β-solidifying TiAl alloy; β-solidifying TiAl alloy; Heat treatment; Additive manufacturing; Creep; Microstructure
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2023.103502

β-solidifying TiAl alloy, an advanced γ-TiAl based alloy, has emerged as a lightweight candidate for high temperature applications in turbine engines. To facilitate the design freedom and manufacturing efficiency, laser-engineered net shaping (LENS) is considered as a promising method to fabricate β-solidifying TiAl alloy components. However, this alloy suffers from cracking during the printing process due to its high brittleness. Hence, grain refinement was introduced to overcome this issue. But, the grain refinement leads to reduction in creep resistance at elevated temperatures. To restore the creep-resistant performance, postproduction heat treatment is required to tailor the mechanical properties of the β-solidifying TiAl alloy. In the present work, the as-printed TiAl alloy is subject to heat treatment with different processes to maximize the formation of α2/γ lamellar structure that corresponds to higher creep resistance. Upon characterizations of the heat treated TiAl alloy samples in terms of microstructure, compressive properties at room temperature and creep resistance at 800 ℃, an optimized two-step heat treatment process comprising of annealing at 1350 ℃ for 1 h followed by air cooling and a subsequent stabilization treatment at 850 ℃ for 6 h is developed. The resultant microstructure consisting of fully lamellar structure with nano-scale lamellar spacing leads to a dramatical increase in the room temperature plasticity of the alloy with respect to the as-printed’s, and high creep resistance at 800 ℃ with applied stress of 150 MPa, which is comparable to the alloys fabricated with conventional casting and wrought technologies. [Display omitted]