| dc.description.abstract | Based on the previously developed Ti65(AlCrNbV)28Zr7 lightweight medium-entropy alloy, minor amount of boron elements were added to create the series of (Ti65(AlCrNbV)28Zr7)100-xBx alloys. The effect of boron content on microstructure evolution and the mechanical properties of these alloys were investigated. Subsequently, the characteristics of alloys were adjusted through thermomechanical heat treatment, and the strengthening mechanism was explored by combining microstructure analyses and mechanical testing.
From the analysis results of using Electron Backscatter Diffraction (EBSD), it was observed that the additions of boron led to a significant refinement in grain size. Furthermore, in B0.6 alloy, many clear precipitates was observed under scanning electron microscopy (SEM). Meanwhile, the hardness of boron-added alloy exhibited an increasing trend from 331 Hv for B0 to 364 Hv for B0.6. Additionally, in the as-cast state, the strength of B0.2 reached 1081 MPa with a ductility of 14%, representing a 7% increase in strength compared with B0. Moreover, the strength of boron-added alloys also increased with increasing boron content, but the ductility show a decreasing trend with increasing boron content.
After annealing of 742°C, 812°C, 854°C, 881°C, respectively heat treatment, it was observed that the (Ti65(AlCrNbV)28Zr7)100-xBx alloy series exhibited increased strength and hardness with increasing the additions of boron under different treatment conditions. Additionally, boron doping was found to inhibit recrystallization behavior in the alloy microstructure, resulting in an elevation of recrystallization temperature. After recrystallization, both B0.2 and B0.1 alloys showed ductility exceeding 20%, while B0.4 and B0.6 presented comparable strength after shorter heat treatment durations. However, with prolonged heat treatment, B0.6 exhibited higher strength than B0.4, reaching 1382 MPa, with a ductility of 14.7%. In summary, considering the mechanical properties among all of the (Ti65(AlCrNbV)28Zr7)100-xBx alloy series, the B0.4 alloy demonstrated the best combination of yield strength and ductility (YS: 1265 MPa, EL: 18.3%).
Keyword: Lightweight medium-entropy alloys, minor element doping, non-equiatomic, thermo-mechanical treatment. | en_US |