Zr/V比例對於TiAlCrZrV中熵合金的微結構及機械性質影響之研究;Effect of Zr/V ratio on the microstructure evolution and mechanical properties of TiAlCrZrV light-weight MEAs

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題名:	Zr/V比例對於TiAlCrZrV中熵合金的微結構及機械性質影響之研究;Effect of Zr/V ratio on the microstructure evolution and mechanical properties of TiAlCrZrV light-weight MEAs
作者:	廖育賢;Liao, Yu-Hsien
貢獻者:	材料科學與工程研究所
關鍵詞:	輕量化中熵合金;固溶強化;熱機處理;異構組織;Lightweight medium-entropy alloys;solid solution strengthening;thermo-mechanical treatment;Heterogenous structure
日期:	2025-07-23
上傳時間:	2025-10-17 11:48:15 (UTC+8)
出版者:	國立中央大學
摘要:	摘要此研究奠基於先前所開發的Ti65(AlCrNbV)35輕量化富鈦中熵合金，透過元素調整，將Nb替換為原子半徑更大且密度更低之Zr，再透過調控Zr與V之比例提升延性，最終製作成Ti65(AlCr)17.5ZrxV17.5-x系列合金，並以此基底研究不同Zr和V比例對於合金之微觀結構及機械性質所帶來的影響，之後再透過熱機處理來增進合金之性能。本研究之合金皆以真空電弧熔煉進行製備，首先將個別成分之原料熔煉成圓錠，再以墜落式鑄造鑄為板材，接著再以XRD分析合金之結構，結果表明，所有合金皆為單一BCC結構，無析出物產生，OM及SEM，之觀察亦能佐證此結果，值得注意的是，鑄造態合金之強度隨著Zr/V比例提升，而有所上升由1088 MPa增加至1245 MPa，但其延伸性亦由24.2%減少至1.9%，而根據計算合金之強度幾乎完全源於固溶強化，其所帶來之強化最高能夠來到1048 MPa，整體而言Zr7V11合金擁有最佳之延性強度平衡有1186 MPa之降伏強度及19.2%之延性。在經歷700°C、800°C及900°C熱機處理後Ti65(AlCr)17.5ZrxV17.5-x系列合金之機械性質皆存在有效地提升，合金之強度會隨著再結晶溫度的提升而有所下降，同時，還能夠觀察到合金之再結晶速度會伴隨著Zr/V比例下降而降低，在800°C之熱處理條件下，Zr9V9及Zr7V11皆能夠在變形帶周圍觀察到許多再結晶晶粒，然而Zr5V13及Zr3V15合金卻難以觀察到再結晶現象產生，得益於此，Zr5V13在800°C的參數下擁有最佳的延性強度組合，其降伏強度高達1369 MPa，其延性也能夠達到17.3%。 ;This study focused on the microstructure and the mechanical properties of light weight Ti65(AlCr)17.5ZrxV17.5-x alloys, which was based on Ti65(AlCrNbV)35 alloy. All alloys were fabricated by arc melting and drop casting technique. While the Ti, Al, and Cr were set at 65, 8.75, and 8.75 at. %, respectively, and the ZrV ratio were modulated from 1 to 0.2. XRD analysis revealed that all as-cast alloys possessed single BCC phase and no second phases could be detectable. Similar results were confirmed by OM and SEM observation. There were no precipitate could be detected in the grain as well as on the grain boundary. However, the EDS Mapping showed that Zr element would segregate on the grain boundary of Zr9V9 alloy. This phenomenon enhanced the yield strength, and caused the embrittlement of alloy. The elongation of Zr9V9 were only 1.9%, but its yield strength could reach 1247 MPa. Aside from the segregation. The yield strength of As-Cast Z/V.02-1 alloy were almost completely composed of solid solution strengthening. Accompany by the increased of Zr/V ratio, the yield strength of Zr3V15-1 alloy raised from 1088 to 1247 MPa, which could totally contribute to the change of δr. According to the calculation, the strength of solid solution would increase from 875 to 1088 MPa with the elevation of δr. Within those alloys, the Zr7V11 exhibited the best strength–ductility synergy. It possessed high yield strength of 1186 MPa and an elongation of 19.2%, which was a 29% increase in strength as compared to Ti65(AlCrNbV)35 alloy. After thermo-mechanical treatment, all alloys still remained single BCC phase. The strength of alloys may gradually decrease with the elevating of recrystallization temperature. In addition, the declining Zr/V ratio would suppress the speed of recrystallization due to the reduced δr. During 800°C recrystallization the Zr5V13 alloy possessed the best strength–ductility synergy. Its yield strength could reach 1369 MPa, while its elongation could still kept at 17.3%. This could be owing to the inhabitation of recrystallization, that caused the perfect match between shear band and recrystallized soft grains.
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