| Summary: | 碩士 === 國立交通大學 === 機械工程系 === 88 === Ti-6Ai-4V is one of the most widely used titanium alloy due to its superior mechanical properties such as high specific strength, excellent fracture toughness, and good corrosion resistance. The application of this alloy spans from airframe structural components, turbine disks and blades to chemical processing equipment. The ELI (extra low interstitials) grade of this alloy has been particularly used in fracture critical environment. This grade also has excellent corrosion resistance and has potential for critical Navy application.
This research was to explore the workability of Ti-6Al-4V ELI through processing map in different thermal gradients. Besides, microscopic observations can be verified through the reliability of the processing map. Series of experiments including thermal gradients testing, compression testing, OM etc., were conducted.
The results of this study showed that the developed processing map is consistent with the observed microstructure. Thus, processing map is an effective approach to determine the optimization of hot forming processes in Ti-6Al-4V ELI. According to the developed processing map, the optimal regions at a true strain of 0.3 for isothermal forging are at (1) around 900℃and 0.01s-1 with 70% efficiency, (2) around 950℃and 3s-1 with 45% efficiency, and (3) around 1100℃and 0.01s-1 with 45% efficiency. The optimal regions for non-isothermal forging are at (1) around 900℃and 0.01s-1 with 75% efficiency, (2) around 900℃and 3 s-1 with 60% efficiency, and (3) around 1100℃and 0.01s-1 with 50% efficiency.
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