Measurement of the Anisotropic Dynamic Elastic Constants of Additive Manufactured and Wrought Ti6Al4V Alloys

Abstract

Additively manufactured (AM) materials and hot rolled materials are typically orthotropic, and exhibit anisotropic elastic properties. This paper elucidates the anisotropic elastic properties (Young’s modulus, shear modulus, and Poisson’s ratio) of Ti6Al4V alloy in four different conditions: three AM (by selective laser melting, SLM, electron beam melting, EBM, and directed energy deposition, DED, processes) and one wrought alloy (for comparison). A specially designed polygon sample allowed measurement of 12 sound wave velocities (SWVs), employing the dynamic pulse-echo ultrasonic technique. In conjunction with the measured density values, these SWVs enabled deriving of the tensor of elastic constants (Cij) and the three-dimensional (3D) Young’s moduli maps. Electron backscatter diffraction (EBSD) and micro-computed tomography (μCT) were employed to characterize the grain size and orientation as well as porosity and other defects which could explain the difference in the measured elastic constants of the four materials. All three types of AM materials showed only minor anisotropy. The wrought (hot rolled) alloy exhibited the highest density, virtually pore-free μCT images, and the highest ultrasonic anisotropy and polarity behavior. EBSD analysis revealed that a thin β-phase layer that formed along the elongated grain boundaries caused the ultrasonic polarity behavior. The finding that the elastic properties depend on the manufacturing process and on the angle relative to either the rolling direction or the AM build direction should be taken into account in the design of products. The data reported herein is valuable for materials selection and finite element analyses in mechanical design. The pulse-echo measurement procedure employed in this study may be further adapted and used for quality control of AM materials and parts.

A Review on Vibration Characteristics of Additively Manufactured Metal Alloys

“…[ 7 ] This gap in understanding was highlighted in a study by Tevet et al, which explored the anisotropy of Ti6Al4V parts fabricated by AM in comparison to conventional methods. [ 113 ] Interestingly, the study revealed only minimal differences in elastic characteristics across various orientations. It is crucial for designers to consider the variation in elastic characteristics resulting from different manufacturing techniques and directions (i.e., AM build direction), because it can significantly affect the vibration response of the built parts.…”

3D-Printed Patient-Customized Artificial Vertebral Body for Spinal Reconstruction after Total En Bloc Spondylectomy of Complex Multi-Level Spinal Tumors

“…Materials used in 3D-printing mainly include titanium alloy, porous tantalum metal, and polyether ether ketone[ 21 - 23 ]. In our study, we used the titanium alloy, Ti 6 Al 4 V, as it offers many useful advantages.…”

Nondestructive measurement of anisotropic elastic constants of selective laser melted 316L based on a tri-mode ultrasonic method

“…When the anisotropic behavior is considered, more information on ultrasonic wave velocities in different directions is required to derive more components in the elastic stiffness matrix. For instance, Tevet et al fabricated specially designed polygon samples to allow measurement of 12 sound wave velocities to determine the anisotropic dynamic elastic constants of AM Ti6Al4V Alloys [21]. A multiple mode ultrasonic transducer and measurement system should be developed to avoid changing the coupling condition and obtain more information on wave velocities.…”