Abstract
The deformation behavior of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe high strength β titanium alloy is systematically investigated by isothermal compression in α + β field with the deformation temperatures ranging from 1003 K to 1078 K, the strain rates ranging from 0.001 s−1 to 1 s−1 and the height reduction is around 50%. Essentially, the flow stress-strain curve of isothermal compression in α + β field exhibits a flow softening feature when the strain rate is higher than 0.1 s−1 as while it exhibits a steady-state feature as the strain rate is lower than 0.1 s−1. The peak stress increases with a decrease in deformation temperature and the increase of strain rate. The activation energy for deformation in α + β field was calculated and the average activation energy of 271.1 kJ/mol. The microstructure observation reveals that the isothermal deformation in the α + β field of the alloy is mainly controlled by the dynamic recovery mechanism accompanied with the secondary dynamic recrystallizitation of β phase. The α phase shows an obvious pinning effect for the movement of dislocations. During deformation, the α phase was elongated and fragmented.
Highlights
Β titanium alloys possess the wide applied range in the applications of aerospace industries due to their excellent mechanical properties [1,2,3]
The isothermal compression experiment was conducted on a Gleeble-1500dD simulator (Dynamic Systems Inc., Poestenkill, NY, USA) at the deformation temperatures ranging from 1003 K to 1078 K with an interval of 25 K, the strain rates of 0.001 s−1, 0.01 s−1, 0.1 s−1, 1 s−1 respectively and the height reduction of 50%
At strain rate of 1 s−1 and temperatures of 1003 K, the curve exhibits an increase in true stress after a broad softening, this may be due to the faster dislocation multiplication than dislocation motion resulting from high strain rate and low temperature
Summary
Β titanium alloys possess the wide applied range in the applications of aerospace industries due to their excellent mechanical properties [1,2,3]. The mechanical properties of β titanium alloys are mainly controlled by microstructure, especially the grain size, volume fraction and morphology of α phase (primary, secondary and grain boundary α) [4,5,6,7]. The mechanical properties of β titanium alloys can be optimized through effectively microstructural controlling during the different stages of thermomechanical processing [9]. Β titanium alloys are forged in the β field to break down the coarse grain microstructure, and forged at the β or α + β field. It should be pointed out that the desired properties of titanium alloys are dependent on the final thermomechanical processing [10,11,12]. The minimal α + β forging should be carried out if a good ductility is required
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