| 摘要: | 這項研究以之前開發的Ti65(AlCrNbV)28Zr7輕量化富鈦中熵合金為基礎，通過添加微量硼元素，製作成(Ti65(AlCrNbV)28Zr7)100-xBx (x=0.1、0.2、0.4、0.6)系列合金，並研究硼元素含量對合金性能的影響。而後，透過熱處理來調節合金的特性，並結合微觀結構和機械性能的分析結果，探討其強化機制。
以電弧熔煉將各成分熔成圓錠，並鑄造成板材後，由EBSD分析結果可知，在硼元素的摻雜對於晶粒有明顯的細化效果，且在SEM下觀察到有析出物的產生，並使合金之硬度由未添加硼元素的331 Hv上升至B0.6的364 Hv，另外，在鑄造態時，B0.2的強度可達到1081MPa，且擁有14 %的延性，強度比未添加硼元素前增加了7 %，而隨著硼含量的增加，其強度有增加的趨勢，但延性也會相對降低。
(Ti65(AlCrNbV)28Zr7)100-xBx系列合金經過熱處理後，發現在不同處理條件下，隨著硼元素的增加，合金的強度和硬度均有所提高。此外，觀察到在材料的微觀結構中，硼元素的摻雜抑制了合金退火後的再結晶行為，進而使得再結晶溫度提高。在進行再結晶退火熱處理之後，B0.2、B0.1延性皆超過20%，而B0.4及B0.6在較短時間的熱處理下呈現相近的降伏強度，然而在拉長熱處理時間後B0.6之降伏強度會高於B0.4，其強度可達1382 MPa，延性則有14.7 %。最後，在(Ti65(AlCrNbV)28Zr7)100-xBx系列合金中，綜合鑄造態之機械性質，B0.4合金具有最佳之降伏強度1265 MPa及延性18.3%的綜合性質。
;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. |
