| 摘要: | 輕量化富鈦中熵合金具有低密度及優異的材料性質等優點，在航太及汽車領域擁有十分良好的前景。本研究基於先前所開發的Ti65(AlCrNbV)35輕量化富鈦中熵合金，以微量硼元素摻雜製備為(Ti65(AlCrNbV)35)100-xBx系列合金，探討硼元素摻雜對合金之影響，並藉由熱機處理來調控合金之性質，再結合微結構及機械性質之分析結果探討其強化機制。
由X-ray繞射分析可知，在硼元素摻雜後，由於硼元素之原子半徑較其他合金元素小，因此繞射峰有往右偏移的情形，且有TiB繞射峰的出現，並使合金之硬度由B0的323 Hv提升至B0.6的378 Hv，在鑄造態時，B0.2擁有1054 MPa的強度及21%的延性，其強度與B0相比增長了17%，B0.4及B0.6由於在晶界中出現大量析出物而使機械性質下降。
(Ti65(AlCrNbV)35)100-xBx系列合金進行熱機處理之後，在X-ray繞射分析中亦可觀察到有硼元素摻雜的合金具有TiB之繞射峰，而在不同熱處理條件下，合金之強度及硬度皆隨硼元素摻雜量上升而提升，且在材料微結構方面發現合金之再結晶行為在硼元素摻雜後受到抑制，使再結晶溫度提高，而在再結晶之後，B0.2、B0.1及B0之延性皆超過20%，而B0.4之強度雖提升至1157 MPa，延性卻下降至10%。最後，可透過將B0、B0.1及B0.2施以適當的熱處理可滿足本研究對機械性質之要求，而在(Ti65(AlCrNbV)35)100-xBx系列合金中，綜合鑄造態之機械性質，B0.2合金具有最佳之降伏強度及延性綜效表現(YS. 1275 MPa, EL. 10%)。
;Lightweight titanium-rich medium-entropy alloys (MEAs) have great potential in the aerospace and automotive industries due to their low density and excellent material properties. In this study, the effect of boron on the microstructure and mechanical properties of the (Ti65(AlCrNbV)35)100-xBx alloy series were investigated. The properties of the alloy were enhanced by thermo-mechanical treatment, and the strengthening mechanism was explored by combining the characterization of microstructure and mechanical properties.
X-ray diffraction analysis reveals that the addition of boron results in a rightward shift of the diffraction peaks due to the smaller atomic radius of boron compared to other elements, and the TiB diffraction peak is also observed. The hardness of the alloy increased from 323 Hv for B0 to 378 Hv for B0.6. In the as-cast state, B0.2 exhibits a strength of 1054 MPa and 21% elongation, which is a 17% increase in strength compared to B0. However, the mechanical properties of B0.4 and B0.6 decreased due to the precipitation at grain boundaries.
After thermo-mechanical treatment, (Ti65(AlCrNbV)35)100-xBx alloy series exhibit TiB diffraction peaks in X-ray diffraction analysis. The strength and hardness increased with an increase of boron content despite various heat treatment conditions. In terms of microstructure, the recrystallization behavior of the alloy tends to be tough by boron doping, resulting in an increase of recrystallization temperature. After recrystallization, the elongation of B0, B0.1, and B0.2 exceeded 20%. Conversely, the elongation of B0.4 decreased to 10% despite its high strength (1157 MPa). Among (Ti65(AlCrNbV)35)100-xBx alloy series, B0, B0.1 and B0.2 can reach the goal of this study through proper heat treatment. Overall, considering the mechanical properties in the as-cast state, B0.2 alloy presents the optima synergy of yield strength and ductility (YS. 1275 MPa, EL. 10%) in the (Ti65(AlCrNbV)35)100-xBx alloy series. |
