Enhanced Mechanical Properties of Lightweight Ti65(AlCrNbV)35 Medium-Entropy Alloys via Microstructure Modification Through Minor B Doping

Po-Sung Chen; Bao-Teng Kuo; Pei-Hua Tsai; Jason Shian-Ching Jang; Chih-Yen Chen; I-Yu Tsao

doi:10.3390/ma18102219

Enhanced Mechanical Properties of Lightweight Ti₆₅(AlCrNbV)₃₅ Medium-Entropy Alloys via Microstructure Modification Through Minor B Doping

Materials (Basel). 2025 May 11;18(10):2219. doi: 10.3390/ma18102219.

Authors

Po-Sung Chen¹, Bao-Teng Kuo¹, Pei-Hua Tsai¹, Jason Shian-Ching Jang^{1

2}, Chih-Yen Chen³, I-Yu Tsao¹

Affiliations

¹ Institute of Materials Science and Engineering, National Central University, Taoyuan 320, Taiwan.
² Department of Mechanical Engineering, National Central University, Taoyuan 320, Taiwan.
³ Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.

Abstract

Because of their low density and excellent material properties, lightweight Ti-rich medium-entropy alloys (MEAs) have great potential for application in the aerospace and automotive industries. This study investigated the effects of B doping on the microstructure and mechanical properties of a (Ti₆₅(AlCrNbV)₃₅)_100-xB_x alloy series. The mechanical properties of the alloys were then enhanced through thermomechanical treatment, and the strengthening mechanism was explored by characterizing the alloys' microstructure and mechanical properties. X-ray diffraction revealed that the (Ti₆₅(AlCrNbV)₃₅)_100-xB_x alloys retained their body-centered cubic structure. However, the addition of B resulted in a rightward shift in the diffraction peaks due to B having a smaller atomic radius compared with the other constituent elements. Weak diffraction peaks corresponding to TiB were discovered in the diffraction patterns for the alloys with 0.4 or 0.6% B content (named B0.4 and B0.6, respectively). The hardness of the homogenized alloys was increased from 321 Hv for the base alloy (B0) to 378 Hv for B0.6. In tensile testing, the homogenized alloy with 0.2% B content (B0.2) exhibited a yield strength of 1054 MPa and 21% elongation, which represented 17% greater strength compared with B0. Conversely, the mechanical properties of B0.4 and B0.6 were poorer due to precipitation at grain boundaries. After thermomechanical treatment, the alloys' strength and hardness increased with increasing B content despite various heat treatment conditions. The recrystallization behavior of the alloys tended to be delayed by B doping, resulting in an increase in the recrystallization temperature. After recrystallization at 900 °C, the elongation of B0, B0.1, and B0.2 exceeded 20%. Of the (Ti₆₅(AlCrNbV)₃₅)_100-xB_x alloys in the series, B0.2 presents the optimal combination of favorable yield strength and ductility (1275 MPa and 10%, respectively).

Keywords: lightweight medium-entropy alloys; minor element doping; nonequiatomic; thermomechanical treatment.

Abstract

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