Numerical analysis of tensile behaviour of Ti-13Nb-13Zr alloy after anodic oxidation

Abstract

The surface of coarse-grained Ti-13Nb-13Zr (CG TNZ) alloy was modified using the anodic oxidation. In order to obtained nanostructured oxide layer, as electrolyte in surface modification process 1M H₃PO₄ + NaF was used, while anodizing time was 90 minutes. The modified surface morphology was analyzed using the field emission scanning electron microscopy (FE-SEM)). It was realized that anodic oxidation led to the creation of the oxide layer consisted of nanotubes. Tensile characteristics of the CG TNZ alloy, before and after anodic oxidation, were determined by tensile testing. Tensile testing was performed using Micro Tensile Specimens (MTS) with a rectangular cross-section. The anodic oxidation led to a decrease of tensile characteristics of the CG TNZ alloy. In order to better understand tensile behaviour of the CG TNZ alloy after anodic oxidation, numerical analysis was done. The 3D numerical model of MTS, which simulated the tensile test, was made in Abaqus software package. Numerical results were obtained using the complete Gurson model (CGM), which is micromechanical model used for the ductile fracture of metallic materials. The parameter that quantifies the damage in the material, that is, the volume fraction of voids or porosity, is varied. So the value of the damage parameter, the initial void volume fraction, f₀, was 0.01 and 0.005. In addition to the elongation of the MTS, the reduction of the cross-sectional thickness at the neck of MTS was also considered. Results showed that CGM for the initial value of the damage parameter 0.005 predicts the failure of the MTS at the corresponding value of thickness reduction.