[SY-F5] Phase field modeling of deformation twinning in β-metastable titanium alloys
Recently, new β-metastable titanium alloys, so-called ''TRIP/TWIP titanium alloys'' (TRIP for TRansformation Induced Plasticity and TWIP for TWinning Induced Plasticity), have been developed to exhibit improved mechanical properties at ambient temperature. These properties are attributed to very complex microstructures engendered by the mechanical destabilization of the initial bcc phase (β) in the course of the deformation. Indeed, the microstructure features numerous twins following the peculiar {332}<113> twinning mode of the β phase, specific to β-titanium alloys, as well as the orthorhombic (α'') phase ensued from concomitant displacive transformations. Moreover, experimental observations revealed the possible activation of secondary deformation mechanisms, i.e. the formation of secondary twins and/or α'' inside primary twins of the β phase.
To get a better understanding of the formation of the complex microstructures described above, we propose a numerical model using the phase field method. This method provides a thermodynamically consistent framework to couple the mechanisms at the origin of the microstructure evolution. As a first step of modeling the evolution of the β-metastable titanium alloys microstructure upon deformation, we focus on the {332}<113> twinning mode of the bcc phase β. In this work, we propose a phase-field model relying on (i) a finite strain formalism; and (ii) the possibility of taking into account the activation of secondary twinning inside primary twins. We will show with simple calculations the capabilities of the model to describe the {332}<113> twin growth. A comparison with a model formulated in a small strain formalism will also be presented to show the influence of the geometrical non-linearities introduced in the finite strain framework.
To get a better understanding of the formation of the complex microstructures described above, we propose a numerical model using the phase field method. This method provides a thermodynamically consistent framework to couple the mechanisms at the origin of the microstructure evolution. As a first step of modeling the evolution of the β-metastable titanium alloys microstructure upon deformation, we focus on the {332}<113> twinning mode of the bcc phase β. In this work, we propose a phase-field model relying on (i) a finite strain formalism; and (ii) the possibility of taking into account the activation of secondary twinning inside primary twins. We will show with simple calculations the capabilities of the model to describe the {332}<113> twin growth. A comparison with a model formulated in a small strain formalism will also be presented to show the influence of the geometrical non-linearities introduced in the finite strain framework.