A high-withdrawing-rate method to control the orientation of (γ+α2) lamellar structure in a β-solidifying γ-TiAl-based alloy

Zhiping Li, Liangshun Luo*, Yanqing Su*, Binbin Wang, Liang Wang, Tong Liu, Mengjia Yao, Chen Liu, Jingjie Guo, Hengzhi Fu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

β-solidifying γ-TiAl-based alloys with well-controlled lamellar orientation possess excellent mechanical properties, and low withdrawing rates are usually used to control the lamellar orientation by directional solidification. Herein, a high-withdrawing-rate method to control the lamellar orientation in a β-solidifying γ-TiAl-based alloy, TNM alloy (Ti-43.5Al–4Nb–1Mo-0.1B at.%), is proposed by Bridgeman directional solidification. Using this method, polysynthetic twinned (PST) single crystal of TNM alloy with a good lamellar controlling result is obtained. The mechanism of lamellar orientation controlling lies in the process of solidification and β/α transformation, which are governed by thermal stabilization treatment and withdrawing rate. Thermal stabilization treatment for 60 min can make the sample maintain stable interfaces of liquid/solid and β/α phase with a high temperature gradient before the withdrawing process starts, and it also leads to the incline of β dendrites; a high withdrawing rate of 100 μm/s can accomplish the grain selection of α phase during β/α transformation and make complete peritectic reaction occur. Compared with as-cast one, PST single crystal specimen has its room-temperature tensile property enhanced greatly, and presents an ultimate tensile strength/strain of 476 MPa/1.75% with a trans-lamellar fracture morphology.

Original languageEnglish
Article number144078
JournalMaterials Science and Engineering: A
Volume857
DOIs
Publication statusPublished - 1 Nov 2022
Externally publishedYes

Keywords

  • Directional solidification
  • Lamellar orientation controlling
  • Phase transformation
  • TiAl-based alloys

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Li, Z., Luo, L., Su, Y., Wang, B., Wang, L., Liu, T., Yao, M., Liu, C., Guo, J., & Fu, H. (2022). A high-withdrawing-rate method to control the orientation of (γ+α2) lamellar structure in a β-solidifying γ-TiAl-based alloy. Materials Science and Engineering: A, 857, Article 144078. https://doi.org/10.1016/j.msea.2022.144078