Characterization of a New Microstructure in a β-Solidifying TiAl Alloy after Air-Cooling from a β Phase Field and Subsequent Tempering

Metals

Guang Yang¹  Emmanuel Bouzy²  Lingyan Sun³  Liang Cheng³  Yalin Lu³  Yi Chen³  Hongchao Kou⁴ 

[1] College of Mechanical and Electrical Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China;LEM3, CNRS UMR 7239, Université de Lorraine, Ile du Saulcy, 57045 Metz CEDEX 1, France;School of Materials and Engineering, Jiangsu University of Technology, Changzhou 710072, China;State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;

关键词: titanium aluminides;    martensitic transformation;    variant selection;    microstructure;    electron back-scattered diffraction;   

DOI  :  10.3390/met8030156

来源: DOAJ

【 摘 要 】

In this study, we found that well-developed α2′ martensite was formed in a Ti-40Al-10V (atomic percent or at.%) alloy after air-cooling from a β phase field, rather than the traditional α2/γ lamellar colonies. The martensitic laths were produced according to the Burgers orientation relationship (OR), the same as those during quenching. Local variant selection detected that three (or six) α2′ variants sharing one (or two) common [11.0]α2′ axes were predominant, while no global variant selection was observed. Subsequent to the martensitic transformation, the retained β phase was decomposed mainly via a β→γ transformation. The γ laths always nucleated at the α2′/β interface according to a Blackburn orientation relationship. In order to stabilize the microstructure, the air-cooled samples were tempered at 800–1000 °C. During tempering, the microstructure decomposed mainly via an α2′→γ transformation. The martensite was almost completely transformed after tempering at 1000 °C for 4 h, and hence a fine β-γ microstructure was obtained. Such a treatment resembling the quenching–tempering in steels may be a new strategy for the microstructural design of TiAl alloys, while an unexpected quenching process can be avoided.

【 授权许可】

Unknown