Correlation between Laser-Ultrasound and Microstructural Properties of Laser Melting Deposited Ti6Al4V/B4C Composites

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.

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Study and classification of the Crystallographic Orientation Distribution Function of a non-grain oriented electrical steel using computer vision system

Journal of Materials Research and Technology ◽

10.1016/j.jmrt.2018.05.028 ◽

2019 ◽

Vol 8 (1) ◽

pp. 1070-1083

Author(s):

Roberto Fernandes Ivo ◽

Douglas de Araújo Rodrigues ◽

José Ciro dos Santos ◽

Francisco Nélio Costa Freitas ◽

Luis Flaávio Gaspar Herculano ◽

...

Keyword(s):

Computer Vision ◽

Distribution Function ◽

Orientation Distribution Function ◽

Crystallographic Orientation ◽

Electrical Steel ◽

Vision System ◽

Orientation Distribution ◽

Computer Vision System

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A continuous net-like eutectic structure enhances the corrosion resistance of Mg alloys

International Journal of Bioprinting ◽

10.18063/ijb.v5i2.207 ◽

2019 ◽

Vol 5 (2) ◽

pp. 49 ◽

Cited By ~ 5

Author(s):

Cijun Shuai ◽

Wenjing Yang ◽

Youwen Yang ◽

Chengde Gao ◽

Chongxian He ◽

...

Keyword(s):

Corrosion Resistance ◽

Eutectic Structure ◽

Mg Alloys ◽

The Other ◽

Laser Melting ◽

Α Phase ◽

Az61 Alloy ◽

Mg17al12 Phase ◽

Good Biocompatibility ◽

Ti Content

Mg alloys degrade rather rapidly in a physiological environment, although they have good biocompatibility andfavorable mechanical properties. In this study, Ti was introduced into AZ61 alloy fabricated by selective laser melting,aiming to improve the corrosion resistance. Results indicated that Ti promoted the formation of Al-enriched eutectic α phaseand reduced the formation of β-Mg17Al12 phase. With Ti content reaching to 0.5 wt.%, the Al-enriched eutectic α phaseconstructed a continuous net-like structure along the grain boundaries, which could act as a barrier to prevent the Mg matrixfrom corrosion progression. On the other hand, the Al-enriched eutectic α phase was less cathodic than β-Mg17Al12 phase inAZ61, thus alleviating the corrosion progress due to the decreased potential difference. As a consequence, the degradationrate dramatically decreased from 0.74 to 0.24 mg·cm-2·d-1. Meanwhile, the compressive strength and microhardness wereincreased by 59.4% and 15.6%, respectively. Moreover, the Ti-contained AZ61 alloy exhibited improved cytocompatibility.It was suggested that Ti-contained AZ61 alloy was a promising material for bone implants application.

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Effects of Briquettes with Different Crack Structures on Propagation Characteristics of Ultrasonic Waves under Wetting Conditions

10.21203/rs.3.rs-72803/v1 ◽

2020 ◽

Author(s):

Gang Wang ◽

Jinzhou Li ◽

Huaixing Li ◽

Zhiyuan Liu ◽

Yanpei Guo ◽

...

Keyword(s):

Particle Size ◽

Ultrasonic Velocity ◽

Bituminous Coal ◽

Ultrasonic Attenuation ◽

Crack Size ◽

Ultrasonic Waves ◽

Ultrasonic Frequency ◽

Propagation Characteristics ◽

Sample Mass ◽

Velocity Increase

Abstract In order to examine the effect of briquettes with different crack structures on ultrasonic characteristics under different wetting conditions, a series of ultrasonic testing are carried out on briquettes at different wetting heights and the ultrasonic characteristics in these coal samples are explored. The results show that ultrasonic amplitude is positively correlated with the emission voltage, whereas ultrasonic frequency is negatively correlated with the emission voltage. Changes in both are closely related to the particle size and density. The ultrasonic velocity is positively correlated with the wetting degree. Sample mass has the greatest effect on the ultrasonic velocity, followed by particle size, and pressure has the smallest effect. At dry stage, ultrasonic velocity in gas coal is less than that in bituminous coal. The opposite is true in the fully wet state. The influence of crack thickness on ultrasonic velocity gradually increases with the wetting degree increasing. At dry stage, the velocity gradually increases with the crack dip increasing, while as the wetting height increasing, magnitude of velocity increase gradually decreases with the dip increasing. The ultrasonic attenuation in the briquettes reduces with the emission voltage enhancing. The attenuation decreases with sample particle size, crack thickness and crack size decreasing and with sample mass, pressure and crack dip increasing. The ultrasonic attenuation shows a trend of increase before decrease with the wetting height increasing. The attenuation of ultrasonic wave increases with wave velocity increasing for intact samples and shows a trend of increase before decrease for cracked samples.

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Crystallographic Orientation Control of 316L Austenitic Stainless Steel via Selective Laser Melting

ISIJ International ◽

10.2355/isijinternational.isijint-2019-744 ◽

2020 ◽

Vol 60 (8) ◽

pp. 1758-1764 ◽

Cited By ~ 3

Author(s):

Takuya Ishimoto ◽

Siqi Wu ◽

Yukinobu Ito ◽

Shi-Hai Sun ◽

Hiroki Amano ◽

...

Keyword(s):

Stainless Steel ◽

Austenitic Stainless Steel ◽

Selective Laser Melting ◽

Crystallographic Orientation ◽

Laser Melting ◽

Orientation Control ◽

316L Austenitic Stainless Steel

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Finite Element Modeling of Selective Laser Melting 316L Stainless Steel Parts for Evaluating the Mechanical Properties

Volume 2: Materials; Biomanufacturing; Properties, Applications and Systems; Sustainable Manufacturing ◽

10.1115/msec2016-8594 ◽

2016 ◽

Cited By ~ 3

Author(s):

Arman Ahmadi ◽

Narges Shayesteh Moghaddam ◽

Mohammad Elahinia ◽

Haluk E. Karaca ◽

Reza Mirzaeifar

Keyword(s):

Mechanical Properties ◽

Finite Element ◽

Stainless Steel ◽

Finite Element Model ◽

Grain Boundaries ◽

Mechanical Response ◽

Element Model ◽

Polycrystalline Materials ◽

Microstructural Properties ◽

Laser Melting

Selective laser melting (SLM) is an additive manufacturing technique in which complex parts can be fabricated directly by melting layers of powder from a CAD model. SLM has a wide range of application in biomedicine and other engineering areas and it has a series of advantages over traditional processing techniques. A large number of variables including laser power, scanning speed, scanning line spacing, layer thickness, material based input parameters, etc. have a considerable effect on SLM process materials. The interaction between these parameters is not completely studied. Limited studies on balling effect in SLM, densifications under different processing conditions, and laser re-melting, have been conducted that involved microstructural investigation. Grain boundaries are amongst the most important microstructural properties in polycrystalline materials with a significant effect on the fracture and plastic deformation. In SLM samples, in addition to the grain boundaries, the microstructure has another set of connecting surfaces between the melt pools. In this study, a computational framework is developed to model the mechanical response of SLM processed materials by considering both the grain boundaries and melt pool boundaries in the material. To this end, a 3D finite element model is developed to investigate the effect of various microstructural properties including the grains size, melt pools size, and pool connectivity on the macroscopic mechanical response of the SLM manufactured materials. A conventional microstructural model for studying polycrystalline materials is modified to incorporate the effect of connecting melt pools beside the grain boundaries. In this model, individual melt pools are approximated as overlapped cylinders each containing several grains and grain boundaries, which are modeled to be attached together by the cohesive zone method. This method has been used in modeling adhesives, bonded interfaces, gaskets, and rock fracture. A traction-separation description of the interface is used as the constitutive response of this model. Anisotropic elasticity and crystal plasticity are used as constitutive laws for the material inside the grains. For the experimental verification, stainless steel 316L flat dog bone samples are fabricated by SLM and tested in tension. During fabrication, the power of laser is constant, and the scan speed is changed to study the effect of fabrication parameters on the mechanical properties of the parts and to compare the result with the finite element model.

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Microstructure and Mechanical Properties of Ti-6Al-4V Alloy Samples Fabricated by Selective Laser Melting

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.770.179 ◽

2018 ◽

Vol 770 ◽

pp. 179-186 ◽

Cited By ~ 2

Author(s):

Jing Bo Gao ◽

Xiao Li Zhao ◽

Ju Kun Yue ◽

Meng Chao Qi ◽

De Liang Zhang

Keyword(s):

Mechanical Properties ◽

Heat Treatment ◽

Crystal Growth ◽

Yield Strength ◽

Selective Laser Melting ◽

Lamellar Structure ◽

Growth Direction ◽

Laser Melting ◽

Α Phase ◽

Dog Bone

Ti-6Al-4V (wt%) alloy samples with dog-bone and box shapes respectively were fabricated by selective laser melting (SLM). The microstructures and mechanical properties of the 3D printed Ti-6Al-4V samples with and without heat treatment were characterized and tested. The microstructures of the as-fabricated dog-bone shaped samples were mainly composed of acicular α’ phase. After annealing at 700°C, the acicular α’ phase changed into an α/β lamellar structure. After solution treatment at 955°C, water quenching and aging at 550°C, the microstructure was mainly composed of primary α phase and α/β lamellar structure. The optimum heat treatment is annealing, and the mechanical properties of the annealed sample are as follows: yield strength: 1015 MPa, ultimate tensile strength (UTS): 1083 MPa and elongation to fracture: 7.9%. The microstructures of the box-shaped samples after annealing mainly consist of α phase and α/β lamellar structure. When stretched along the direction parallel to the crystal growth direction, the yield strength and UTS of the sample are 1054 and 1090 MPa，and its elongation to fracture is 6.3%. When stretched along the direction perpendicular to the crystal growth direction, the yield strength and UTS of the sample are 1019 and 1068 MPa respectively, and its elongation to fracture is 8.7%.

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Ultrasonic Characterization of the Elastic Constants in an Aging Ti-6Al-4V ELI Alloy

Volume 11: Acoustics, Vibration, and Phononics ◽

10.1115/imece2019-10194 ◽

2019 ◽

Author(s):

Hector Carreon

Keyword(s):

Elastic Properties ◽

Ultrasonic Velocity ◽

Precipitation Process ◽

Material Microstructure ◽

Clear Trend ◽

Sem Image ◽

Wave Velocities ◽

Ultrasonic Characterization ◽

Α Phase

Abstract In this paper, we report the experimental data of the elastic properties of the young and shear modulus based on the variation in the ultrasonic velocity parameter during the microstructural evolution in a Ti-6Al-4V alloy with two varying microstructures, bimodal and acicular respectively. The two different initial microstructures, were treated thermally by aging at 515°C, 545°C and 575°C at different times from 1 min to 576hr to induce a precipitation process. Ultrasonic measurements of shear and longitudinal wave velocities, scanning electron microscopy (SEM) image processing, optical microscopy (OM) and microhardness were performed, establishing a direct correlation with the measurements of the ultrasonic velocity and the elastic properties developed during the thermal treatment of the artificial aging. The results of the ultrasonic velocity show a very clear trend as the aging time progresses, which is affected by precipitation of Ti3Al particles inside the α phase. In this way, we can know, in a fast and efficient way, the elastic properties developed during the heat treatment of aging at long times, since the presence of these precipitates hardens the material microstructure affecting the final mechanical properties.

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