Fracture characteristics of Ti-6Al-4V and Ti-5Al-2.5Fe with refined microstructure using hydrogen
- Toyohashi Univ. of Technology (Japan)
- Academia Sinica, Shenyang (China)
- Sumitomo Metals Industries, Co., Ltd., Jyouetsu (Japan). Naoetsu Works
The hydrogenation behavior of Ti-6Al-4V, with the starting microstructures of coarse equiaxed {alpha} and coarse Widmanstaetten {alpha}, respectively, was investigated under a hydrogen pressure of 0.1 MPa at temperatures between 843 and 1,123 K. The hydrogen content was determined as a function of hydrogenation time, hydrogenation temperature, and hydrogen flow rate. The phases presented in the alloy after hydrogenation were determined with X-ray and electron diffraction analysis in order to define the effect of Thermochemical Processing (TCP) on the microstructure of the alloy. Mechanical properties and fracture toughness of Ti-6Al-4V and Ti5Al-2.5Fe subjected to the various TCP were then investigated. Hydrogenation of Ti-6Al-4V with the starting microstructure of coarse equiaxed {alpha} at 1,023 K, just below hydrogen saturated {beta} (denoted {beta} (H)) transus temperature, produces a microstructure of {alpha}, orthorhombic martensite (denoted a{double_prime} (H)) and {beta} (H). Hydrogenation at 1,123 K, above {beta} (H) transus, results in a microstructure of a{alpha}{double_prime} (H) and {beta} (H). Microstructure refinement during TCP results mainly from decomposition of {alpha}{double_prime} (H) and {beta} (H) into a fine mixture of {alpha} + {beta} during dehydrogenation. An alternative TCP method is below {beta} (H) transus hydrogenation (BTH), consisting of hydrogenation of the alloy below the hydrogenated {beta} (H) transus temperature, air cooling to room temperature, and dehydrogenation at a lower temperature, which is found to improve mechanical properties significantly over a conventional TCP treatment.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 72786
- Journal Information:
- Metallurgical Transactions, A, Journal Name: Metallurgical Transactions, A Journal Issue: 5 Vol. 26; ISSN 0360-2133; ISSN MTTABN
- Country of Publication:
- United States
- Language:
- English
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