The Study of Solution and Aging Treatment of Ti-6Al-4V and its Post-Vacuum-Brazing
| Autor: | Kuo-Hsun Lee, 李國勳 |
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| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 In this research, the popular alloy Ti-6Al-4V was used to investigate the optimization process parameters of heat-treatment by using Taguchi method. The hardness after aging and tensile strength was chosen as the quality characteristics. Eight controllable factors were selected including fan, solution temperature, duration time of solution treatment, protective gas, quench delay time, cooling rate, temperature and duration time of aging treatment. The experiment was performed using orthogonal array of L18(21×37). The best combination condition of process parameters was obtained after Taguchi quality analysis. The quality reproducibility was verified to be excellent via the confirmation experiments. The results showed that the hardness after aging was above HRc 43, the tensile strength of rod material all above 1,165Mpa(169ksi), and that of plate material all above 1,082Mpa(157ksi) while using the optical heat-treatment condition. They all met the specification of AMS-4965 for the quality requirement of alloy Ti-6Al-4V. Using the optimal solution and aging treatment for Ti-6Al-4V brazed by Ti-15Cu-15Ni and Ag-26.7Cu-4.5Ti fillers, the average shear strengths of the lap-joint interface are 427 to 521MPa and 441 to 488Mpa, respectively. When compared to the reference, the shear strength has improved by 16% and 240%. And the average grain sizes of post-brazed solution and aging treatment are approximately between 6.6 μm to 8.1μm and 5.3 μm to 6.1 μm, and the average lengths of Widmanstätten structure are approximately between 37μm to 40μm and 25 μm to 35 μm with ≦ 1μm in width, which are significantly smaller than that of post-brazed annealing. Both Ti-base and Ag-base fillers specimens are examined to indicate the improving mechanism for shear strength of brazed joints is by optimal post-brazed solution and aging treatment, as it is an effective way to homogenize the microstructure of Ti-6Al-4V joint to simultaneously enhance the strength of joint braze and substrate. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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