Effect of interference laser treatment on the surface region homogeneity of a biomedical β-Ti alloy

This study provides a detailed insight into the microstructure and chemical composition of a surface region of a novel, metastable Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy with a low Young’s modulus modified by Direct Laser Interference Patterning (DLIP) using an Nd:YAG (1064 nm) with 10 ns pulse duration. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy, and Scanning Transmission Electron Microscopy (STEM) were employed to investigate the microstructure of the cross-section of modified TNTZ. For chemical composition analysis of the surface region, X-ray Photoelectron Spectroscopy (XPS) and Atom Probe Tomography (APT) were applied. The chemical composition analysis was divided into two stages: surface analysis (XPS and APT) and analysis of a bulk (APT at the depth of 300 nm). Through the interference phenomenon during DLIP treatment, we observed significant microstructure evolution in the surface region of TNTZ alloy — grain refinement on the tops of the grooves while the microstructure at the bottoms was unattached. APT measurements at the depth of 300 nm revealed a noticeable local chemical heterogeneity of the substrate alloy, that has not been considered before when designing the metastable β-Ti systems. The applied laser treatment homogenizes the remelted zones and thus provides an additional factor influencing the surface properties.