Papers by Keyword: Titanium

Abstract: Optimizing the mechanical properties of aluminum to titanium welds is crucial to establish applications for dissimilar lightweight structures in the aerospace industry. In this context, solid-state welding technologies have proven effective in terms of short joining cycles, allowing the combination of cost-effective production and structural weight optimization. However, metallurgical effects between aluminum and titanium in the joint interface are still not completely understood due to differences in physical as well as chemical characteristics. In this study, aluminum alloy 6013 was welded to Ti6Al4V by refill Friction Stir Spot Wel ding, including systematic variations of Mg and Si alloying element content in the used AA6013 sheets. In total five different Al alloys were welded to the titanium to investigate the influence of Mg and Si during processing. Apart from the material selection, the weld strength is mainly influenced by the intermetallic compound thickness at the interface, which in turn primarily depends on the exposed temperature cycle. Consequently, major interest during this study was given on the temperature evolution, interfacial features and the global mechanical properties.

Abstract: This research work focuses on the atomic study of hexagonal titanium (Ti) in order to estimate the relative accuracy of DFT (Density Functional Theory) and Molecular Statics (MS) approaches to better understand the interactions between solute atoms and twins. Four twins (2 tensile twins and 2 compressive twins) were modeled and then doped with the following elements: hydrogen, oxygen, nitrogen, aluminum and vanadium (H, O, N, Al, V). The formation energies of the twins as well as the segregation energies of the solute atoms were calculated to better predict the concentration heterogeneities of these elements in the material and their possible influence on local mechanical properties.

Abstract: Laser powder bed fusion (LBPF) is currently the most mature metal additive manufacturing (AM) technology. While it does not have the same flexibility as directed energy deposition techniques to produce compositional gradients, LPBF can still be used to generate bimetallic parts by depositing one metal on a build plate made of another. Here, we print combinations of Ti-6Al-4V with Ta and characterize defects that occur at the interface. We use thermodynamic modeling to explain the formation of keyhole porosity and solidification cracks when Ta is built on a Ti baseplate, and the lack of defects when the materials are reversed. By understanding the mechanisms that lead to defect formation, the methodology demonstrated here can be applied to other material systems to efficiently design bimetallic LPBF processes.

Abstract: Biomaterials are significantly required for medical technology. Hydroxyapatite (HA) is a bioactive material and is an excellent candidate for use as a bone replacement or bone repair material. Because HA has similar properties to human bone. However, the disadvantage of HA is its low mechanical strength. Titanium (Ti) is the famous material used to strengthen the strength of HA. This is because Ti can be used in the human body without causing undesirable reactions. The development of Ti-HA composite materials provides a bioactive material with high-strength properties. The homogeneous microstructure of materials, which is essential for achieving the required properties, can be accomplished by using composite particles as the starting materials. This research aims to develop the Ti-HA composite particles by mechanical alloying method. The mixture of Ti and HA in a mass ratio of 70:30 (Ti:HA) was milled by using a high-energy mill, i.e., a vibration mill, at a speed of 750 and 1000 rpm for 30, 60, 120, 180 and 300 minutes without inert gas supply. The results show that the Ti-HA composite particles were produced by using a vibration mill. HA particles completely cover the surface of Ti. No phase change of Ti and HA was observed under all milling conditions except at 1000 rpm for 300 minutes. The tiny XRD peaks of TiO were observed. This study developed an effective and low-cost method for producing Ti-HA composite particles, which is advantageous to engineering and medical technology.

Abstract: There is a growing demand in the dental implant sector which aims to recreate the exact function and appearance of natural teeth, including strength, textures, and seamless blending with nearby teeth. Therefore, choosing the best crown material is a vital and challenging decision. To address this challenge, current study employs a comprehensive approach using Finite Element Analysis (FEA) on a 3-D CAD model. The stress analysis was carried out on three different crown materials - commercially pure Titanium (cp Ti), Zirconia (ZR), and Lithium Disilicate (LD) and compared their performance with that of human tooth material. The computational analysis results reveal that the pure Titanium (cp Ti) crown has shown the least deformation while the LD crown has showed the highest deformation under same loading conditions. When maximum stress is compared, Titanium showed the highest value, followed by Zirconia, whereas Lithium Disilicate (LD) demonstrated stress and deformation levels comparable to those of natural teeth.

Abstract: The effects of heat treatment in different ambient pressures or oxygen concentration on the wettability of the titanium (Ti) surface were examined. Polished titanium plates were heat-treated at various temperatures and periods in the pressure-controlled or oxygen concentration-controlled atmospheres. The wettability was evaluated by water contact angle measurement. The X-ray photoelectron spectroscopy was performed on the heat-treated and stored Ti surface to analyze adsorbates and surface products. The heat-treated Ti in the atmospheric air became hydrophilic due to the desorption of hydrocarbons on the surface. Then, the adsorption of hydrocarbons during storage in the atmospheric air returned its wettability to that before heating. On the other hand, the heat-treated Ti in a vacuum (low ambient pressures) or low oxygen concentration became hydrophobic due to an increase in the CH/OH (hydrocarbon/hydroxyl group) ratio on the surface. The wettability of hydrophobized Ti retained its wettability during storage in the atmospheric air.

Abstract: This presentation provides an overview of the recent collaboration between CSIRO and The Boeing Company focused on developing preforms of high-temperature titanium alloys. This collaboration devised a new method for manufacturing preforms, shaped intermediates and mill products directly from titanium powder. These preforms can then undergo thermomechanical processing to produce parts requiring minimal surface finishing with the desired microstructure and mechanical properties.

Abstract: Due to its low density, high strength to weight ratio, and been unreactive to the human body, titanium is commonly used in human bone implants. Titanium in bone implants can be used in its porous form because the porosity reduces the elastic modulus of the implant, near to that of human cortical or trabecular bone, which prevents the effects of stress-shielding. To date, majority of the published studies using the space holder (SH) method to produce porous titanium, utilized-45 μm titanium hydride dehydride (Ti-HDH) powder, or similar titanium powder. However, there is limited research conducted on the use of coarse titanium powder particles, such as-150 μm Ti-HDH powder to produce porous titanium. Fine Ti-HDH powders are known to have higher oxygen content than coarse Ti-HDH powders, thus the specimens produced from fine powders are harder, require higher compaction pressures and are expected to have lower impact resistance. The following study thus investigated the use of-150 μm Ti-HDH powder to produce porous titanium specimens, by the SH method. The porous specimens of 45 mm diameter were produced by uniaxially compacting mixtures of sodium chloride (NaCl) powder and Ti-HDH powder at 500 MPa. The NaCl powder utilized was hand sieved to a range of-500 μm. The specimens were sintered at 1150 for 4 hours in a high-vacuum tube furnace. Three porosity levels were investigated i.e. 40%, 50% and 60%. The sintered compacts were assessed for density, porosity and elastic moduli. It was found that the sintered porosity of the specimens ranged from 42.7-59.1%, and the sintered density ranged from 1.84-2.58 g/cm³. The elastic moduli of the specimens were found to reduce as the porosity increased, and ranged from 0.59-1.3 GPa, which is similar to the elastic moduli of human trabecular bone. The use of-150 μm Ti-HDH powder is thus potentially a lower cost alternative, than the use of-45 μm Ti-HDH powder, to produce porous titanium for human bone implants.

Abstract: For the processing of metal powders by Metal Injection Moulding (MIM) or indirect methods of Additive Manufacturing (AM), such as material extrusion (MEX-AM) polymers of different kinds are employed. Usually, the task of these polymers is to enable the shaping of a certain geometry and to maintain this shape down to the first cohesive effects of sintering. Nowadays, for the production of metal parts one goal is to get rid of the polymer as complete as possible. Another possibility is to use the polymer or at least part of it, mainly the carbon, for the metallurgical process of forming the final part in sintering as a process of heat treatment. Titanium is a metal, which is reacting with carbon easily. The question in focus here is how to utilise the carbon or some of it in the powder metallurgical processing of titanium. For first steps into this question, we selected two different powders, CPTi and TiH₂, and mixed them with two different polymers, polypropylene PP and low-density polyethylene LDPE. As a compatibilizer stearic acid SA was used. The polymers were selected because they are normally used as backbone in binder systems, and show a significantly different thermal degradation behaviour. Thus, the amount and type of carbon during thermal degradation could be expected to be different. The study comprises the preparation of polymer-powder blendings with up to 80 vol.% powder to resemble the conditions after solvent debinding; the shaping in discs, and TG-DTA experiments in air and in Ar to find out the temperature of backbone removal (Tr). Isothermal experiments are also done to know about the polymer removal with time. The different interaction of the polymers with the titanium powders is investigated, with a special attention to the interaction of hydride decomposition and polymer degradation. Keywords: Metal Injection Moulding; indirect Additive Manufacturing; titanium and titanium alloys; powder-polymer interaction

Abstract: Additive Manufacturing technologies revolutionize the production of 3D components by selectively depositing material layers, facilitating intricate geometries and cavities with minimal material waste. Among these techniques, Plasma Metal Deposition (PMD) stands out as a powder-based method offering promising applications, particularly in the aerospace sector.In this study, five specimens manufactured via PMD have been investigated, employing a base material of Grade 2 titanium and a welding material comprising a powder blend of grade 1 titanium and 30% B₄C particles. The incorporation of boron carbide aims to further augment the already commendable properties of titanium, catering to the stringent requirements of the aerospace industry.Attention is directed towards key manufacturing parameters such as the transferred arc and torch travel speed, while maintaining fixed parameters including pilot arc, current, and torch-substrate height. The primary objective of this research is to comprehensively explore the PMD technique, scrutinizing potential thermodynamic reactions during the welding process between titanium and boron carbide. Concurrently, thorough characterization of the specimens will be conducted to elucidate their properties.This project seeks to optimize the PMD manufacturing process and enhance the performance characteristics of the produced parts, thereby addressing critical needs in the aerospace sector. By unravelling the intricacies of thermodynamic interactions and material properties, we aim to pave the way for advancements in additive manufacturing methodologies and the production of high-performance titanium components for aerospace applications