Laser powder bed fusion (LPBF) of commercially pure titanium and alloy development for the LPBF process.

Laser powder bed fusion (LPBF) of titanium or titanium alloys allows fabrication of geometrically more complex and, possibly, individualized implants or osteosynthesis products and could thus improve the outcome of medical treatments considerably. However, insufficient LPBF process parameters can result in substantial porosity, decreasing mechanical properties and requiring post-treatment. Furthermore, texturized parts with anisotropic properties are usually obtained after LPBF processing, limiting their usage in medical applications. The present study addresses both: first, a design of experiments is used in order to establish a set of optimized process parameters and a process window for LPBF printing of small commercially pure (CP) titanium parts with minimized volume porosity. Afterward, the first results on the development of a biocompatible titanium alloy designed for LPBF processing of medical implants with improved solidification and more isotropic properties are presented on the basis of conventionally melted alloys. This development was performed on the basis of Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au, a near-α alloy presented by the authors for medical applications and conventional manufacturing, with yttrium and boron additions as additional growth restriction solutes. In terms of LPBF processing of CP titanium grade 1 powder, a high relative density of approximately 99.9% was obtained in the as-printed state of the volume of a small cubical sample by using optimized laser power, scanning speed, and hatch distance in combination with a rotating scanning pattern. Moreover, tensile specimens processed with these volume settings and tested in the as-printed milled state exhibited a high average yield and ultimate tensile strength of approximately 663 and 747 N/mm2, respectively, combined with a high average ductility of approximately 24%. X-ray diffraction results suggest anisotropic mechanical properties, which are, however, less pronounced in terms of the tested specimens. Regarding alloy development, the results show that yttrium additions lead to a considerable microstructure refinement but have to be limited due to the occurrence of a large amount of precipitations and a supposed higher propensity for the formation of long columnar prior ß-grains. However, phase/texture and microstructure analyses indicate that Ti-0.44O-0.5Fe-0.08C-0.4Si-0.1Au-0.1B-0.1Y is a promising candidate to achieve lower anisotropy during LPBF processing, but further investigations on LPBF printing and Y2O3 formation are necessary.

Tensile Deformation Behaviors of Pure Ti with Different Grain Sizes under Wide-Range of Strain Rate.

In this study, pure titanium equivalent to Grade 1 was subjected to tensile tests at strain rates ranging from 10-6 to 100 s-1 to investigate the relationship between its mechanical properties and its twinning and slip. Deformation properties and microstructures of samples having average grain sizes of 210 µm (Ti-210), 30 µm (Ti-30), and 5 µm (Ti-5) were evaluated. With increasing strain rates, the 0.2% proof stress and ultimate tensile strength increased for all samples; the fracture strain increased for Ti-210, decreased for Ti-5, and changed negligibly for Ti-30. Comparing high (100 s-1) and low (10-6 s-1) strain rates, twinning occurred more frequently in Ti-30 and Ti-210 at high strain rates, but the frequency did not change in Ti-5. The frequency of 1st order pyramidal slip tended to be higher in Ti-30 and Ti-5 at low strain rates. The higher ductility exhibited by Ti-210 at high strain rates was attributed to the high frequency of twinning. In contrast, the higher ductility of Ti-5 at low strain rates was attributed to the activity of the 1st order pyramidal slip.

Dataset for deformation behavior of pure titanium grade 2 materials during continuous extrusion.

There is a huge application and demand for titanium alloys with excellent upgraded mechanical, metallurgical, and material properties in modern industries. To fulfill the demand of modern industries metal forming process is highly desirable. Among all metal forming processes, a special type of cold forming called the continuous extrusion process has been highly appropriate to fulfill the demands. The theoretical analysis has been carried out through Upper Bound Method. The numerical simulation has been carried out through the three-dimensional finite element tool DEFORM-3D. The experimental plan and design have been carried out using Taguchi (2^3) array methods on the MINITAB platform by considering extrusion wheel velocity and feedstock temperature as chief extrusion parameters. The experimental validation process was executed on 12.5 mm CP- Titanium grade 2 feedstock materials using a TBJ350 CONFORM machine setup. The optimization process of parameters for the optimum value of the response variable was carried out through Grey Relational Analysis.

Nanofunctionalization of Additively Manufactured Titanium Substrates for Surface-Enhanced Raman Spectroscopy Measurements.

Powder bed fusion using a laser beam (PBF-LB) is a commonly used additive manufacturing (3D printing) process for the fabrication of various parts from pure metals and their alloys. This work shows for the first time the possibility of using PBF-LB technology for the production of 3D titanium substrates (Ti 3D) for surface-enhanced Raman scattering (SERS) measurements. Thanks to the specific development of the 3D titanium surface and its nanoscale modification by the formation of TiO2 nanotubes with a diameter of ~80 nm by the anodic oxidation process, very efficient SERS substrates were obtained after deposition of silver nanoparticles (0.02 mg/cm2, magnetron sputtering). The average SERS enhancement factor equal to 1.26 × 106 was determined for pyridine (0.05 M + 0.1 M KCl), as a model adsorbate. The estimated enhancement factor is comparable with the data in the literature, and the substrate produced in this way is characterized by the high stability and repeatability of SERS measurements. The combination of the use of a printed metal substrate with nanofunctionalization opens a new path in the design of SERS substrates for applications in analytical chemistry. Methods such as SEM scanning microscopy, photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD) were used to determine the morphology, structure and chemical composition of the fabricated materials.

Wear and Corrosion Resistance of AlSi10Mg-CP-Ti Metal-Metal Composite Materials Produced by Electro-Sinter-Forging.

Metal-metal composites are a class of composite materials studied for their high ductility and strength, but their potential applications are currently limited by the complex manufacturing processes involved. Electro-sinter-forging (ESF) is a single-pulse electro discharge sintering technique that proved its effectiveness in the rapid sintering of several metals, alloys, and composites. Previous studies proved the processability of Ti and AlSi10Mg by ESF to produce metal-metal composites and defined a correlation between microstructure and processing parameters. This paper presents the wear and corrosion characterizations of two metal-metal composites obtained via ESF with the following compositions: 20% Ti/80% AlSi10Mg and 20% AlSi10Mg/80% Ti. The two materials showed complementary resistance to wear and corrosion. A higher fraction of AlSi10Mg is responsible for forming a protective tribolayer in dry-sliding conditions, while a higher fraction of Titanium confers improved corrosion resistance due to its higher corrosion potential.

Effect of loading frequency on cyclic fatigue lifetime of a standard-diameter implant with an internal abutment connection.

OBJECTIVE: To investigate the effect of loading frequency on the fatigue lifetime of one standard-diameter titanium dental implant system. METHODS: Thirty-six titanium dental implant specimens (Bone Level RC, Straumann) were assembled following manufacturer's instructions and torqued into cylindrical holder blocks following the apparatus specified by the ISO 14801 test standard. Stainless steel loading hemispheres were bonded on the abutments with a moment arm of 11mm. The holder blocks had layers of differing stiffness to simulate human jaw bone. Constant-stress fatigue lifetime testing was conducted at two frequencies (2Hz and 15Hz) with a stress ratio of 0.1 until fracture in deionized water at 37°C on servo-hydraulic load frames (MTS). The fractured specimens were retrieved and examined using fractographic technique to determine the failure mode. The lifetime data were fit to a general log-linear regression model. RESULTS: The coefficient for the load amplitude term of the regression model indicated that increasing load amplitude had a statistically significant negative effect on the fatigue lifetime. The coefficients for the cyclic frequency term and the load-frequency interaction term were not significantly different from zero, which indicated that increasing loading frequency did not have an influence on the number of cycles to failure. Fractographic analysis showed that all specimens exhibited an identical combined fracture of abutment and abutment screw adjacent to the bone level. SIGNIFICANCE: Higher loading frequency at least up to 15Hz may be used for future studies of some implant systems to improve the efficiency of fatigue testing.

Effects of acid-treatment conditions on the surface properties of the RBM treated titanium implants / 대한치과재료학회지

The purpose of this study was to evaluate the effect of acid-treatment conditions on the surface properties of the RBM (Resorbable Blast Media) treated titanium. Disk typed cp-titanium specimens were prepared and RBM treatments was performed with calcium phosphate ceramic powder. Acid solution was mixed using HCl, H2SO4 and deionized water with 4 different volume fraction. The RBM treated titanium was acid treated with different acid solutions at 3 different temperatures and for 3 different periods. After acid-treatments, samples were cleaned with 1 % Solujet solution for 30 min and deionized water for 30 min using ultrasonic cleanser, then dried in the electrical oven (37℃). Weight of samples before and after acid-treatment were measured using electric balance. Surface roughness was estimated using a confocal laser scanning microscopy, crystal phase in the surface of sample was analyzed using X-ray diffractometer. Surface morphology and components were evaluated using Scanning Electron Microscope (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoemission Spectroscopy (XPS). Values of the weight changes and surface roughness were statistically analyzed using Tukey-multiple comparison test (p=0.05). Weight change after acid treatments were significantly increased with increasing the concentration of H₂SO₄ and temperature of acid-solution. Acid-treatment conditions (concentration of H₂SO₄, temperature and time) did not produce consistent effects on the surface roughness, it showed the scattered results. From XRD analysis, formation of titanium hydrides in the titanium surface were observed in all specimens treated with acid-solutions. From XPS analysis, thin titanium oxide layer in the acid-treated specimens could be evaluated. Acid solution with 90℃ showed the strong effect on the titanium surface, it should be treated with caution to avoid the over-etching process.

Titanium removable denture based on a one-metal rehabilitation concept.

The use of a single metal for all restorations would be necessary because it protects against metal corrosion caused by the contact of different metals. For this "one-metal rehabilitation" concept, non-alloyed commercially pure (CP) titanium should be used for all restorations. Titanium frameworks have been cast and used for the long term without catastrophic failure, whereas they have been fabricated recently using computer-aided design/computer-aided manufacturing (CAD/CAM). However, the milling process for the frameworks of removable partial dentures (RPDs) is not easy because they have very complicated shapes and consist of many components. Currently, the fabrication of RPD frameworks has been challenged by one-process molding using repeated laser sintering and high-speed milling. Laser welding has also been used typically for repairing and rebuilding titanium frameworks. Although laboratory and clinical problems still remain, the one-metal rehabilitation concept using CP titanium as a bioinert metal can be recommended for all restorations.

The effect of veneer on the marginal fit of the copings using different materials / 实用口腔医学杂志

Objective:To compare the marginal fit changes between after-and before-veneering of the copings using three kinds of materials:gold alloy,cp titanium and Ni-Cr alloy,so as to determine whether the fit changes was influenced with the veneer and their clinical significance.Methods:24 maxillary incisor acrylic resin PFM abutments fabricated by machine with the consolidated standard were divided into three groups,each abutment was waxed-up,invested,and casted with three kinds of materials:gold alloy,cp titanium and Ni-Cr alloy.For all groups,the copings were repositioned on their respective abutments,the marginal fit values of four points of each coping were measured.Furthermore,after three groups of copings were veneered with recommended porcelain,marginal fit values of same point of each abutment were remeasured.SAS software was used to carry out statistical analysis.Results:One way analysis of variance of marginal fit values revealed significant differences between before and after veneering in three groups,and the marginal fit value enhanced after veneered.Among three groups,cp titanium group had a significant difference when compared with other two groups(P