熱機處理對TiAlNbCrVZr系高熵合金微結構和機械性質影響之研究;Thermomechanical treatment on the microstructure and mechanical properties of TiAlNbCrVZr high-entropy alloy

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題名:	熱機處理對TiAlNbCrVZr系高熵合金微結構和機械性質影響之研究;Thermomechanical treatment on the microstructure and mechanical properties of TiAlNbCrVZr high-entropy alloy
作者:	徐聖家;Shiu, Sheng-Jia
貢獻者:	材料科學與工程研究所
關鍵詞:	輕量化高熵合金;非等原子比;熱機處理;light-weight HEAs;non-equiatomic;thermomechanical treatment
日期:	2021-07-26
上傳時間:	2021-12-07 11:52:43 (UTC+8)
出版者:	國立中央大學
摘要:	本研究目的為設計密度接近5 g/cm3、降伏強度能達到1200 MPa以及塑性能維持15 %以上之高熵合金，首先將數種高熔點且密度較低之元素，用高溫電弧融煉技術鑄成具有簡單固溶相之六元TiAlCrVNbZr系列高熵合金，觀察Zr元素含量對整體微結構與機械性質之影響，並透過滾軋製程使其厚度降低並累積應變能，再將其以短時間退火熱處理使材料晶粒細化，藉由分析微結構與機械性質探討其強化機制，找出最合適的加工製程與熱處理參數。研究結果顯示，鑄造態的TiAlCrVNbZr系列皆為單一BCC相，並能達到 1000 MPa以上的降伏強度與20.0 %以上的拉伸塑性。另外將此系列合金以熱機處理強化，發現給予冷滾軋試片較大的加工量，在熱處理後能得到較佳的機械性質組合。此外在冷滾軋前合金材料可藉由熱滾軋製程提高整體之延展性。本實驗中得到最佳的加工製程參數是先將材料進行50 %熱滾軋，再透過70 %冷滾軋，退火熱處理後TiAlCrVNbZr3、TiAlCrVNbZr5及TiAlVCrNbZr7皆能達到期望之機械性能，其中又以Ti65AlCrVNbZr7成分有最良好的機械性質，在熱處理後能達到1351 MPa的降伏強度與15.3 %的拉伸塑性，TiAlVCrNbZr10因再結晶溫度發生較早導致強度下降較快，在本實驗設計參數中無法達成預期目標，顯示隨合金之鋯元素含量增加，退火時再結晶抵抗能力減弱。 ;The purpose of this experiment is to design a high entropy alloy with density close to 5 g/cm3, yield strength of 1200 MPa and plastic strain maintained above 15%. First, several elements with high melting point and low density such as Ti, Al, V, Cr, Nb and Zr. They are cast into a alloy with simple solid solution phases by vacuum metallurgy and rapidly solidification technology. Moreover, the main strengthening mechanism is carried out through the rolling process. It can reduce the thickness of alloy and accumulate the strain energy in it. Then through annealing heat treatment in a short time to refine the grain of the material. Finally, by analyzing the microstructure and mechanical properties to explore the strengthening mechanism, and find the most suitable processing and heat treatment parameters. According to the tensile test results, as-cast TiAlCrVNbZr series are all single BCC phases. And, they can achieve yield strength above 1000 MPa and tensile ductility above 20.0%. In addition, this series of alloys were strengthened by thermomechanical treatment. And applying a larger amount of processing to the cold-rolled test pieces can possess mechanical properties after heat treatment. The best processing parameters obtained in this experiment are to reduce the thickness of the alloy material by 50 % first by hot rolling, and then reduce the thickness by 70 % by cold rolling. After processing annealing, TiAlCrVNbZr3, TiAlCrVNbZr5 and TiAlVCrNbZr7 can achieve the desired mechanical properties. Among them, the optimum mechanical performance occurs at TiAlCrVNbZr7 with tensile yield strength of 1363 MPa and plastic strain of 16.3 % after heat treatment. TiAlVCrNbZr10 due to the earlier recrystallization temperature caused the strength to drop quickly. The expected target cannot be achieved in the design parameters of this experiment. It shows that as the zirconium content of the alloy increases, the resistance to recrystallization is weakened during annealing.
顯示於類別:	[材料科學與工程研究所 ] 博碩士論文

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