TEMPERATURE DEPENDENCE OF UNSTABLE PLASTIC FLOW AND MULTI-NECKING IN ELI Ti-5Al-2.5Sn ALLOY

摘要

Ti-5Al-2.5Sn extra-low-interstitial (ELI) alloy is widely used as a structural material in cryogenic engineering because of its outstanding mechanical behaviour, especially at low temperatures. ELI Ti-5Al-2.5Sn exhibits unstable plastic flow (load drops) at very low temperatures (below 40K). The influence of temperature and sequential straining on load drops in tensile stress-strain curves are investigated. Multi-necking is detected in the static tensile experiments of ELI Ti-5Al-2.5Sn. Cryogenic temperature is of crucial importance to the occurrence of this phenomenon. Transmission electron microscopy (TEM) results are presented to discuss the possible reason of multi-necking. In additional, an optical method is used to gauge the geometry of multi-necking specimens.