Micromechanical modeling of the effect of elastic and plastic anisotropies on the mechanical behavior of β-Ti alloys

Safaa Lhadi (1, 2) , Stéphane Berbenni (1, 2) , Nathalie Gey (1, 2) , Thiebaud Richeton (1, 2) , Lionel Germain (1, 2)

1 LEM3 - Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux
2 Labex DAMAS

Near β-titanium alloys like Ti-5553 or Ti-1023 often exhibit bimodal phase constituents embedded in a retained β-phase matrix, which represents up to 40% of the volume. The highly elastic anisotropic β-phase may strongly influence the mechanical behavior of these alloys. The present work models the effect of the coupled role of β-phase elastic and plastic anisotropies on the local and overall responses of a fully β-phase polycrystalline aggregate like the Ti-17 alloy. The model is based on an advanced elasto-viscoplastic self-consistent (EVPSC) homogenization scheme solved by the "translated field" method together with an affine linearization of the viscoplastic flow rule. The effects of elastic anisotropy, crystallographic texture and grain morphology are theoretically studied during uniaxial tensile tests, tension-compression tests as well as multiaxial plastic yielding. First, it is shown that different sets of elastic constants taken from literature give rise to similar effective responses but to widely scattered incompatibility stresses. During uniaxial tensile loading, the highest local incompatibility stresses are achieved in <111> oriented grains at the end of the elastic regime. Likewise, the effect of the β-grain morphology for realistic grain aspect ratios is seen to be weak on the overall behavior but strong on incompatibility stresses. In addition, the elastic anisotropy can have a significant influence on yield surfaces for β-forged textured polycrystals. Finally, the simulated Bauschinger stress monotonically increases with the elastic anisotropy coefficient for a random texture while it may be reduced in case of β-forged texture due to a competition between elastic and plastic sources of incompatibility stresses.

Mots clés: elastic anisotropy; elastic/plastic incompatibilities; Elasto-Visco-Plastic Self-Consistent (EVPSC) scheme; polycrystalline β-Ti; affine approximation; translated fields method

Domaines: Mécanique des matériaux [physics.class-ph]

Safaa Lhadi, Stéphane Berbenni, Nathalie Gey, Thiebaud Richeton, Lionel Germain. Micromechanical modeling of the effect of elastic and plastic anisotropies on the mechanical behavior of β-Ti alloys. International Journal of Plasticity, 2018, 109, pp.88-107. ⟨10.1016/j.ijplas.2018.05.010⟩. ⟨hal-02353021⟩