Ti-6Al-4V plastic deformation at low temperatures: a FEM analysis beyond the onset of instability

Abstract

In order to assess the life of Ti-6Al-4V components at 20 K supporting local plastic deformation during nominal loading, it is necessary to quantitatively describe the effect of the induced heat generation. Linear stability analysis is applied to describe the onset of instability for the experimental conditions considered. Then, the thermomechanical coupling is implemented in a finite element code. It is shown that the model properly describes the experimental tensile tests performed at 20 K under helium gas. It is able to restore the main features described in the literature. The model is applied to discuss the development of the heterogeneous pattern of deformation through the specimen at various imposed cross-head velocities. The transition from propagative to random non-propagative localized bands is observed. The proposed finite element model is shown to be a powerful tool to analyse in-service components in the cryogenic range.

Thermal Effects During Tensile Deformation of Ti‐6Al‐4V at Different Strain Rates

“…However, despite the importance of thermal softening, when the effect of strain rate is studied, heat losses and temperature in the deforming specimen are not studied in detail, and isothermal or adiabatic conditions are assumed without a clearly defined criterion. Regarding temperature, most studies focus on relatively high or low temperatures , while the effect of small deviations from room temperature is not considered. However, the study of this temperature range is especially interesting.…”

Mechanical characterization of Ti–5Al–2.5Sn ELI alloy at cryogenic and room temperatures

“…To improve the predictive capability of the model, Zaiser combined the said thermo-mechanical instability with a description of dislocation dynamics. As pointed out by Briottet et al (2001), this coupling mainly affects the response of single crystals; the macroscopic behavior of instabilities leading to discontinuous yielding in polycrystals can be instead modeled allowing for the thermo-mechanical feedback only.…”

A new constitutive model for HCP metals

“…Lee and Lin [14] studied the temperature sensitivity of the flow stress of Ti6Al4V during high temperature deformation and fracture. Briottet et al [15] observed the instability phenomenon of plastic deformation of Ti6Al4V under tension. Poletti et al [16] studied the hot deformation of Ti6Al4V under compression, in which the local deformation parameters were correlated with the microstructural characteristics though not at high strain rates.…”