Abstract
The precise characterisation of hot flow behavior of titanium alloys is of vital importance for practical hot forming processes. To precisely determine the hot flow behavior of titanium alloys under the forming conditions, Gleeble hot tensile tests are usually performed to simulate the forming processes by accurately controlling the deformation temperatures and strain rates under designed conditions. However, there exists a non-uniform temperature distribution during the Gleeble tests, which leads to inaccuracies in the determined hot flow behavior. To overcome such an issue, this paper proposed a new strain-based correction method for Gleeble hot tensile tests, enabling the mitigation of the non-uniform temperature-induced stress-strain curve inaccuracies. The non-uniform temperature zones have been successfully excluded in the calculation of the true strain levels. A series of hot uniaxial tensile tests of TA32 at temperatures, ranging from 750 °C to 900 °C, and strain rates, 0.01/s~1/s, were carried out. The obtained stress-strain correlations for a large gauge zone were characterized using the new correction method, which was further used to evaluate the hardening behavior of titanium alloys. The results have shown that the ductility, strain hardening component (i.e., n), strain rate hardening component (i.e., m) and uniform strain value (i.e., εu) are over-estimated, compared to conventional method. Higher strain rates and lower temperature leads to enhanced hardening behavior. This research provides an alternative correction method and may achieve more accurate stress-strain curves for better guidance of the hot forming process for titanium alloys.
Highlights
Titanium alloys are advanced materials with a superior strength-to-weight ratio and high corrosion resistance [1,2] and have been widely applied in the aerospace, marine and transportation industries
The success forming of thin-walled structures is normally indicated by the uniform thickness of the formed components without any defects. This largely depends on the material hardening and softening behavior at the designed deformation temperature
Lower strain rates lead to longer deformation time and, a longer time soaking at high deformation temperatures
Summary
Titanium alloys are advanced materials with a superior strength-to-weight ratio and high corrosion resistance [1,2] and have been widely applied in the aerospace, marine and transportation industries. TA32 titanium alloy, as a conventional type of titanium alloy, is widely used to form load-bearing thin-walled structures. The success forming of thin-walled structures is normally indicated by the uniform thickness of the formed components without any defects. This largely depends on the material hardening and softening behavior at the designed deformation temperature. Material hot flow behaviors at designed temperature and strain rate ranges shall be thoroughly investigated [8,9,10]. Hot tensile tests at fixed temperatures and strain rates are a commonly used method to characterise hot flow behavior [11] and to investigate hardening phenomena, i.e., strain. Hot uniaxial tensile tests at various temperatures and strain rates were performed. SSppeecciimmeenn ooff GGlleeeebbllee hhoott uunniiaaxxiiaall tteennssiillee tteesstt ((AAllll ddiimmeennssiioonnss aarree iinn mmmm))
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