Authors: Martina Dikovits Cecilia Poletti Fernando Warchomicka
Publish Date: 2013/11/07
Volume: 45, Issue: 3, Pages: 1586-1596
Abstract
The hot formability of a nearβ titanium alloy is studied near the β transus temperature to determine the mechanisms of deformation Compression tests of Ti5Al5Mo5V3Cr1Zr are carried out using a Gleeble®1500 device between 1036 K and 1116 K 763 °C and 843 °C and strain rates between 0001 and 10 s−1 The achieved flow data are used to calculate the efficiency of power dissipation the strain rate sensitivity and instability parameters derived from different models Constitutive equations are built using the stress values at the strain of 04 Light optical microscopy and EBSD measurements are used to correlate the parameters that describe formability with the microstructure It is found that hot deformation is achieved by dynamic recovery in the β phase by subgrain formation Geometric dynamic recrystallization along the β grain boundaries takes place at large deformations high temperatures and low strain rates On the other hand for high strain rates continuous dynamic recrystallization by lattice rotation already starts at a local strain of 1 Different phenomenological models are used to predict the flow instabilities where the flowsoftening parameter α i provides the best correlation with microstructure as well as the physical understanding The instabilities observed in this alloy are strongly related to flow localization by adiabatic heatThe authors would like to thank to the FWF Austrian Science Fund for supporting project P22238N22 Böhler Schmiedetechnik for the provision of the material and the USTEM Vienna University of Technology for the provision of the FEGSEM EBSD facilities
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