Mechanical Behavior of Ti-6Al-2Sn-4Zr-2Mo Titanium Alloy under Hot and Superplastic Forming Conditions: Experiment and Modeling

摘要

Titanium alloys are widely used in the aircraft industry. In sheet form, they can be used for the manufacturing of pylon or engine parts. With the aim of achieving a cost reduction, this study proposes to act on the starting microstructure so as to improve the mechanical properties during the forming stages. In the present study, investigations are focused on Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy, which is especially used for the hot areas (e.g. parts close to the engine or the combustion chamber). A thorough mechanical test campaign was performed on the Ti6242 alloy, examining, on the one hand, the microstructure qualified by the aircraft industry and, on the other hand, a new range of refined microstructures obtained by a hot straining process. For each test, microstructural observations exhibited complex phenomena simultaneously including both grain growth and dynamic recrystallization. The occurrence, sequencing and coupling of the mechanisms were all strongly dependent on the starting microstructure and the test conditions (time-temperature and strain rate) investigated. They are not easy to understand and require further tests and observations. In such a framework, the implementation of mechanical models is an efficient and relevant way of gaining a better knowledge of the microstructural evolution observed and its influence on the mechanical behavior.