Stress partitioning in a near-β Titanium alloy induced by elastic and plastic phase anisotropies: experimental and modeling

¹ Laboratoire d’Étude des Microstructures et de Mécanique des Matériaux, Université de Lorraine, CNRS, Arts et Métiers Paris Tech, LEM3, F-57000 Metz, France
² Institut de Recherche Technologique Materiaux, Metallurgie, Procedes (IRT M2P), 4 Rue Augustin Fresnel, 57070 Metz, France
³ PIMM, CNRS UMR 8006, Arts et Métiers ParisTech, CNAM, 151 Bd de l’Hôpital, 75013 Paris, France
⁴ Laboratory of Excellence on Design of Alloy Metals for Low-mAss Structures (DAMAS), Université de Lorraine, France

^* *Corresponding author: ravi.purushottam-raj@irt-m2p.fr

Abstract

The load transfer induced by the elastic and plastic phase anisotropies of a Ti–10V–2Fe–3Al titanium alloy is studied. The microstructure consists in α nodules embedded in elongated β grains. EBSD performed on the alloy shows no crystallographic texture neither for α nor β phase. Tensile tests along the elongation direction, at a strain rate of 2 x 10^-3 s^-1 give a yield stress of 830 MPa with 13% ductility.

Simulations based on an advanced two-phase polycrystalline elasto-viscoplastic self-consistent (EVPSC) model predict that the β phase first plastifies with a sequential onset of plasticity starting from <110> oriented β grains, then <111> and finally <100> oriented β grains. This leads to a strong load transfer from the β grains to the α nodules whose average behavior remains elastic up to high stresses (~940 MPa). However, additional simulations considering exclusively β grains of specific orientation show that the behavior of α nodules is strongly dependent on the β texture in which they are embedded. Especially, in <001> β grains, which plastify the latest, the model predicts the onset of plasticity in favorably orientated α nodules. Moreover, the orientation spread within the β grains can modify the average plastic behavior of α phase. In future, these results will be compared to data obtained from in-situ High Energy XRD and SEM/EBSD experiments.