Abstract
The presence of large microtextured clusters (MTC) composed of small α-phase crystallites with preferred crystallographic orientations in 3D printed near-α titanium alloys leads to poor mechanical and fatigue properties. It is therefore crucial to characterize the size of MTCs nondestructively. Ti6Al4V/B4C composite materials are manufactured using Laser Melting Deposition (LMD) technology by adding an amount of nano-sized B4C particles to the original Ti6Al4V powder. TiB and TiC reinforcements precipitating at grain boundaries stimulate the elongated α crystallites and coarse columnar MTCs to equiaxed transition, and microstructures composed of approximately equiaxed MTCs with different mean sizes of 11–50 μm are obtained. Theoretical models for scattering-induced attenuation and centroid frequency downshift of ultrasonic waves propagating in such a polycrystalline medium are presented. It is indicated that, the studied composite material has an extremely narrow crystallographic orientation distribution width, i.e., a strong degree of anisotropy in MTCs. Therefore, MTCs make a dominant contribution to the total scattering-induced attenuation and spectral centroid frequency downshift, while the contribution of fine α-phase crystallites is insignificant. Laser ultrasonic inspection is performed, and the correlation between laser-generated ultrasonic wave properties and microstructural properties of the Ti6Al4V/B4C composites is analyzed. Results have shown that the deviation between the experimentally measured ultrasonic velocity and the theoretical result determined by the Voigt-averaged velocity in each crystallite is no more than 2.23%, which is in good agreement with the degree of macroscopically anisotropy in the composite specimens. The ultrasonic velocity seems to be insensitive to the size of MTCs, while the spectral centroid frequency downshift is approximately linear to the mean size of MTCs with a goodness-of-fit (R2) up to 0.99. Actually, for a macroscopically untextured near-α titanium alloy with a relatively narrow crystallographic orientation distribution, the ultrasonic velocity is not correlated with the properties of MTCs, by contrast, the central frequency downshift is dominated by the size and morphology of MTCs, showing great potentials in grain size evaluation.
Highlights
IntroductionMetal 3D printing technology, as an additive manufacturing technology, has the advantages of high deposition efficiency, low manufacturing cost, and a high degree of design freedom, lightweight design and functional integration over the conventional formative or subtractive manufacturing [1,2,3,4]
Laser melting deposited Ti6Al4V/boron carbide (B4 C) composite specimens composed of approximately equiaxed microtextured clusters (MTC) formed by finer α crystallites with preferred orientations were obtained by adding an amount of nano-sized B4 C particles to the original Ti6Al4V powder
Theoretical investigations showed the scattering-induced attenuation and the spectral centroid frequency downshift were closely related with the texture parameter, σ, which accounts for the crystallographic orientation distribution width
Summary
Metal 3D printing technology, as an additive manufacturing technology, has the advantages of high deposition efficiency, low manufacturing cost, and a high degree of design freedom, lightweight design and functional integration over the conventional formative or subtractive manufacturing [1,2,3,4]. It shows broad prospects for technological industrialization in the fields of medical, automotive, nuclear power, and aerospace [4,5]. The LMD with powder feed gives better resolution and surface finish and it has the advantages of high matrix bonding strength, and uniform and dense microstructure
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
