Impact of the Loading Conditions and the Building Directions on the Mechanical Behavior of Biomedical β-Titanium Alloy Produced In Situ by Laser-Based Powder Bed Fusion

Abstract

In order to simulate micromachining of Ti-Nb medical devices produced in situ by selective laser melting, it is necessary to use constitutive models that allow one to reproduce accurately the material behavior under extreme loading conditions. The identification of these models is often performed using experimental tension or compression data. In this work, compression tests are conducted to investigate the impact of the loading conditions and the laser-based powder bed fusion (LB-PBF) building directions on the mechanical behavior of β-Ti42Nb alloy. Compression tests are performed under two strain rates (1 s−1 and 10 s−1) and four temperatures (298 K, 673 K, 873 K and 1073 K). Two LB-PBF building directions are used for manufacturing the compression specimens. Therefore, different metallographic analyses (i.e., optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), electron backscatter diffraction (EBSD) and X-ray diffraction) have been carried out on the deformed specimens to gain insight into the impact of the loading conditions on microstucture alterations. According to the results, whatever the loading conditions are, specimens manufactured with a building direction of 45∘ exhibit higher flow stress than those produced with a building direction of 90∘, highlighting the anisotropy of the as-LB-PBFed alloy. Additionally, the deformed alloy exhibits at room temperature a yielding strength of 1180 ± 40 MPa and a micro-hardness of 310 ± 7 HV0.1. Experimental observations demonstrated two strain localization modes: a highly deformed region corresponding to the localization of the plastic deformation in the central region of specimens and perpendicular to the compression direction and an adiabatic shear band oriented with an angle of ±45 with respect to same direction.

Experimental and numerical investigations of cutting forces and chip formation during precision cutting of Ti42Nb titanium alloy produced by laser-based powder bed fusion

“…The chemical composition of the Ti42Nb titanium alloy investigated in this work is presented in Table 1. The LB-PBF parameters such as laser power, scanning speed, scanning spacing and layer thickness are described in a previous communication [5]. In order to investigate the possible impact of anisotropy, two building directions are used for manufacturing the compression and micro-cutting specimens.…”

“…According to the results, the Ti42Nb microstructure is composed of non-columnar elongated β-grains oriented along the building direction. The as-LB-PBFed Ti42Nb microstructure shows the presence of un-melted or partially melted Nb particles (tomography analyses prove that the un-melted Nb particles represent less than 1% of the total amount of the Nb mass in the alloy see [5]) and spherical and elliptical pores distributed over all the specimens. These pores do not have preferential nucleation sites.…”

Flow-through Gas Phase Photocatalysis Using TiO2 Nanotubes on Wirelessly Anodized 3D-Printed TiNb Meshes

“…Among others, such more complicated 3D Ti substrates can be produced using additive manufacturing. However, though additive manufacturing offers the fabrication a plethora of different shapes, rather few studies have shown their modification with TNT layers. ,− These have been mainly pure Ti and biomedical Ti6Al4V alloy with the aim of their application as implants. − However, also TiNb-based alloys have been shown to be producible using additive manufacturing, by using either selective laser melting (SLM)/laser-based powder bed fusion (LB-PBF), − or laser engineered net shaping (LENS)/laser directed energy deposition. , Direct ink writing (DIW) has so far not been used for the production of TiNb alloys, although DIW has the advantage of simple powder blending, microstructural control through the sintering regimen, and using just the amount of metal powder needed for printing, thus reducing the environmental footprint and production cost …”