Titanium Alloy Powder Research Articles

Thermomechanical processing of a high strength metastable beta titanium alloy powder, consolidated using the low-cost FAST-forge process

The high strength titanium alloy Ti-5553 has been fully consolidated and thermomechanically processed from powder using the FAST-forge process, in only three steps, both at the small and the pilot scale. Titanium alloy components are conventionally produced using a time-consuming process, which involves carbo-chlorination extraction of TiO2, triple vacuum arc re-melting, and multiple thermomechanical and heat treatment steps, before machining. The proposed FAST-forge processing route for titanium alloy components cuts out or significantly reduces these stages, and uses field-assisted sintering technology (FAST) to consolidate powder. This paper assesses the effectiveness of the process for a conventionally used high-strength beta titanium alloy, Ti-5553. Ti-5553 has been fully consolidated by the FAST process at two different dwell temperatures, 850 and 1000°C, and for a 30min dwell time. Small-scale upset forging of cylinders machined from each FAST condition has been performed at forging temperatures 785, 810 and 835°C, and strain rates 0.01, 0.1, 1 and 5s−1, in order to examine the flow stress behaviour. The flow behaviour of both FAST-produced Ti-5553 specimens was found to be very similar to conventionally produced Ti-5553, and the forged microstructures were also comparable. Large-scale forging has been performed on three double truncated cones machined from a FAST specimen produced at a temperature of 1000°C with a 30min dwell time. The cones were forged at 785, 810 and 835°C, and at a strain rate of approximately 3s−1. Each forged specimen was heat treated for 4h at a proprietary temperature between 750 and 850°C, and aged for 8h at a proprietary temperature below 650°C in an inert atmosphere, before air cooling to room temperature. The forged microstructures and heat treated microstructures were found to be comparable to that of conventionally produced Ti-5553. Microhardness measurements of the heat treated specimens, with averages of between 410 and 417Hv, were higher than that of conventionally produced Ti-5553, and were very consistent despite variations in strain and forging temperature. Successful scale-up of the process for a metastable beta titanium alloy indicates its potential to be utilised at an industrial scale.

Titanium powder developments for AM – A round-up

As additive manufacturing/3D printing (AM) has grown rapidly over the last several years, interest in titanium and titanium alloy powders has increased dramatically. This has been reflected in the number of presentations on titanium powders related to AM in recent PM conferences. The publication of the POWDERMET2017 conference proceedings in Advances in Powder Metallurgy & Particulate Materials – 2017 gives an opportunity to include some of the presentations it was impossible to report in previous articles due to conflicting session schedules.

Shear band formation and wear mechanism of titanium alloy powder metallurgy material prepared by HIP using Ti-6Al-4V pre-alloy powder

In this paper, wear mechanism model and shear plane formation model were built based on the influence of residual micro-void of powder metallurgy material on chip-tool interaction and serrated chip shear plane. In the wear mechanism model, the micro-void in the chip back surface tore and accumulated adhered workpiece material in sticking and sliding zones, respectively. In the occasional random shear model, the micro-void increased the change rate of the speed component near the micro-void to cause the shear plane shifts to the micro-void. Ti-6Al-4V powder metallurgy material was prepared with hot isostatic pressing technology to carry out machining experiment. The wear mechanism model and the occasional random shear model were verified with the research on micro-fluctuation of cutting force, wear morphology of cutting tool, and cross section of serrated chip.

Effect of powder surface state on microstructure and tensile properties of a novel near α-Ti alloy using hot isostatic pressing

In this work, a novel near α high temperature titanium alloy powder compact was prepared through hot isostatic pressing (HIP). The effect of powder surface state on microstructure and tensile properties of hot isostatically pressed (HIPed) powder compacts were investigated. The results show that the tensile properties of powder compact HIPed from short-term stored powder are comparable to those of wrought state and the commercial IMI 829 alloys. The relationship between the thickness of oxide layer on the powder surface and powder storage time has been confirmed. The long-term stored powder will increase the microstructural inhomogeneity and reduce the elongation of HIPed powder compacts. The relevant mechanisms were discussed based on the evolutions of powder surface state during powder storage and HIP processes.

Review of the Methods for Production of Spherical Ti and Ti Alloy Powder

Spherical titanium alloy powder is an important raw material for near-net-shape fabrication via a powder metallurgy (PM) manufacturing route, as well as feedstock for powder injection molding, and additive manufacturing (AM). Nevertheless, the cost of Ti powder including spherical Ti alloy has been a major hurdle that prevented PM Ti from being adopted for a wide range of applications. Especially with the increasing importance of powder-bed based AM technologies, the demand for spherical Ti powder has brought renewed attention on properties and cost, as well as on powder-producing processes. The performance of Ti components manufactured from powder has a strong dependence on the quality of powder, and it is therefore crucial to understand the properties and production methods of powder. This article aims to provide a cursory review of the basic techniques of commercial and emerging methods for making spherical Ti powder. The advantages as well as limitations of different methods are discussed.

Biomechanical Properties of 3-Dimensional Printed Volar Locking Distal Radius Plate: Comparison With Conventional Volar Locking Plate

This study evaluated the biomechanical properties of a new volar locking plate made by 3-dimensional printing using titanium alloy powder and 2 conventional volar locking plates under static and dynamic loading conditions that were designed to replicate those seen during fracture healing and early postoperative rehabilitation. For all plate designs, 12 fourth-generation synthetic composite radii were fitted with volar locking plates according to the manufacturers' technique after segmental osteotomy. Each specimen was first preloaded 10 N and then was loaded to 100 N, 200 N, and 300 N in phases at a rate of 2 N/s. Each construct was then dynamically loaded for 2,000 cycles of fatigue loading in each phase for a total 10,000 cycles. Finally, the constructs were loaded to a failure at a rate of 5 mm/min. All 3 plates showed increasing stiffness at higher loads. The 3-dimensional printed volar locking plate showed significantly higher stiffness at all dynamic loading tests compared with the 2 conventional volar locking plates. The 3-dimensional printed volar locking plate had the highest yield strength, which was significantly higher than those of 2 conventional volar locking plates. A 3-dimensional printed volar locking plate has similar stiffness to conventional plates in an experimental model of a severely comminuted distal radius fracture in which the anterior and posterior metaphyseal cortex are involved. These results support the potential clinical utility of 3-dimensional printed volar locking plates in which design can be modified according the fracture configuration and the anatomy of the radius.

Effect of atomization pressure on the breakup of TA15 titanium alloy powder prepared by EIGA method for laser 3D printing

TA15 titanium alloy powder was prepared by Electrode Induction Melting Gas Atomization (EIGA) method at different gas pressure. The breakup behavior of molten droplet in the primary and secondary breakup process was analyzed. Also, the properties of TA15 fine powder prepared at optimized gas pressure were tested. Results shown that gas pressure played a positive role on the transformation between large size oval metal flake and regular molten stick in primary breakup process. After then, the molten stick followed three kinds of breakup modes and turned to disparate shape powders in secondary breakup process, which were normal necking down breakup mode, interfere breakup mode and impact breakup mode. At 6MPa pressure, simulation shown that the back-flow area had the largest volume and the average velocity on the flow field axis reached to 260 m/s. The preparation rate of fine TA15 powder was 82% and had the narrow particle size distribution. The phase of fine powder prepared at 6MPa was all the α-Ti phase. Flow ability and apparent density were 22.1s/50 g and 2.82 g/cm3 respectively, which was conformed to the ASTM test standard and was in line with the requirement for Laser 3D printing.

Three-dimensional thermal analysis of multi-layer metallic deposition by micro-plasma transferred arc process using finite element simulation

Manufacturing of complex 3D-parts by micro-plasma transferred arc (μ-PTA) powder deposition process involves repeated heating and cooling at the same location causing thermal distortion and residual stresses in the substrate and deposited material. Simulation of temperature distribution, thermal cycles and temperature gradient can be helpful to predict thermal distortion and residual stresses. This paper describes 3D-analysis of temperature distribution and thermal cycles in multi-layer metallic deposition by μ-PTA process by finite element simulation using temperature dependent properties of the deposition material. Analysis was also done to study influence of deposition direction on temperature distribution and temperature gradient in multi-layer metallic deposition. The simulated results were experimentally verified on the μ-PTA process experimental apparatus developed for temperature measurement depositing powder of titanium alloy (Ti-6Al–4V) on substrate of the same material. Good agreement is observed between the simulated and experimental results. The results showed that temperature increases with increase in the deposition height and the temperature gradient in parallel deposition is higher than that in back and forth deposition. This implies that parallel deposition exhibits better heat diffusion than back and forth deposition. This work will be helpful in selection of optimum heat input, process parameters and deposition direction in multi-layer metallic deposition by μ-PTA process.

Set of Measures for Improving the Quality of Powders Based on Titanium for Additive Technology

The change in morphology of polygonal powder in a low-temperature plasma generated in an arc discharge is an effective means for resolving the problem of preparing titanium alloy powder of spherical shape used in additive technology. A method is studied for preparing spherical powder of titanium and its alloys by spheroidization in streams of a polygonal powder thermal plasma, prepared by hydrogenation-dehydrogenation. A production scheme is proposed for preparing spherical titanium alloy powder for additive technology, including remelting of certified waste, ingot hydrogenation, crushing, screening its fractions, dehydrogenation, and gas centrifugal classification with final plasma treatment. A technology is developed for preparing spherical titanium alloy powder used in additive technology, with a reduced dissolved gas content. Methods are considered for improving the quality of spheroidized titanium powder including: minimization of the amount of particles with size less than 10 μm in the original polygonal powder, a change in composition of the plasma-forming gas, and prevention of contact with air by powder before and after spheroidization.

Application of additive electron beam technologies for manufacture of parts of VT1-0 titanium alloy powders

Application of additive electron beam technologies for manufacture of parts of VT1-0 titanium alloy powders

Применение аддитивных электроннолучевых технологий для изготовления деталей из порошков титанового сплава ВТ1-0

Применение аддитивных электроннолучевых технологий для изготовления деталей из порошков титанового сплава ВТ1-0

Ultrasonic hot powder compaction of Ti-6Al-4V

Power ultrasonic has been recently employed in a wide variety of manufacturing processes among which ultrasonic assisted powder compaction is a promising powder materials processing technique with significant industrial applications. The products manufactured by the powder metallurgy commonly consist of residual porosities, material impurities, structural non-homogeneities and residual stress. In this paper, it is aimed to apply power ultrasonic to the hot consolidation process of Ti-6Al-4V titanium alloy powder in order to improve mechanical properties. To do this, the effects of ultrasonic power and process temperature and pressure were considered and then deeply studied through a series of experiments. It was shown that the addition of ultrasonic vibration leads to a significant improvement in the consolidation performance and the mechanical strength of the fabricated specimens.

Solid State Manufacture of High Entropy Alloys-Preliminary Studies

For the past ten years Metalysis have produced tantalum, titanium and titanium alloy powders for high performance applications using their solid state salt electrolysis process. This low energy and environmentally friendly process is now being used to manufacture the next generation of High Entropy Alloys (HEAs). In most cases the manufacture of HEAs involves high temperatures which put all of the alloying elements into the liquid phase. This can lead to numerous problems and restrict the number of HEAs which can be made, particularly the alloys where one needs to combine low melting point elements with refractory elements and also where there are significant liquid density differences between the constituents causing melt segregation. The aim is to present the preliminary work carried out by Metalysis and to show how the solid state diffusion process based on molten salt electrolysis lends itself to the industrial scale manufacture of the next generation of HEAs. This study will focus on the HEAs whose constituent alloying elements have large differences in both their melting points and liquid densities, for example, chromium, niobium, tantalum, titanium and aluminum.

Influence of grinding on service properties of VT-22 powder applied in additive technologies

Powder of titanium alloy (VT-22) produced by plasma-spraying was subjected to grinding to obtain powder with size less 100 microns. These powders were sprayed by plasma unit using two types of gases, namely, air and air with methane (spraying in water and sputtering of coating on steel support). Influence of grinding time on yield of powder of required fraction was studied. Morphology and phase composition of the grinded powder and plasma sprayed one were under investigation. In the result of experiments, it appears that the grinding time genuinely influences the chemical and phase compositions, but there is no effect on physical-processing properties. For powders after plasma spraying some changes of non-metal elements content were detected by chemical analysis. Using gaseous mixture of air and methane in plasma spraying unit leads to formation of a new phase in the powder according X-ray diffraction data.

FAST-forge − A new cost-effective hybrid processing route for consolidating titanium powder into near net shape forged components

Reducing the high cost of titanium to a level where it can compete with currently used commodity metals offers opportunities to many industries to exploit its excellent combination of properties to improve performance or reduce weight. The key to decreasing cost is to reduce the number of processing steps to go from ore to component, as well as material wastage from excessive machining. This paper describes a new solid-state hybrid manufacturing route, termed by the authors as FAST-forge, for converting titanium alloy powder into components with wrought properties in two steps; utilising field assisted sintering technology (FAST) to produce a shaped preform billet that is finished to near net shape by a one-step precision hot forge. The route has been demonstrated at the laboratory scale using Ti-6Al–4V hydride-dehydride powder by producing fully consolidated, microstructurally homogeneous, double truncated cone specimens directly through FAST, which were then upset forged at a range of temperatures and strain rates. The microstructural evolution and forging behaviour of the Ti-6Al–4V after FAST consolidation is similar to conventional melt, multi-step forged product. Break up of primary α at high strains was observed at 950°C and 0.01s−1, 0.1s−1, and 1s−1. There is good agreement between finite element modelling of the hot forging and the experimental data, which will enable more complex shaped geometries to be produced via the proposed FAST-forge route in future. Such a route could be used to consolidate powder from a lower-cost alternative extraction method to become a disruptive technology that will enable a step-change in the economics of titanium components.

Mesoscale modelling of selective laser melting: Thermal fluid dynamics and microstructural evolution

In this paper, an integrated computational materials science approach for selective laser melting (SLM) at the mesoscale is presented. A particle dropping model was developed to simulate the representative powder-bed particle distribution of a measured titanium alloy powder. Thermal fluid flow and resulting microstructural evolution of a set of laser scanned single tracks with different powder layer thicknesses and scanning speeds during SLM were also studied using both computational and experimental approaches. The simulated powder particle distribution was found to be consistent with experimental measurement. The thermal fluid flow model predicts that single laser scanned tracks become increasingly irregular-shaped with increased powder layer thickness and increased laser scanning speed. These findings were reinforced by scanning electron microscopy analysis. The more dispersed dissipation of the localised heat for thicker powder layers is understood to cause increased melting and evaporation. This can lead to increased Marangoni force and recoil pressure which in turn destabilises the melt flow. The use of an argon atmosphere speeds up the solidification process when compared with air but does not affect the morphology of single tracks significantly. The predicted microstructure was consistent with the electron backscattered diffraction data. The microstructure-based modelling methodology considering the representative powder size distribution provides a good predictive capability for the laser-powder interaction behaviour, surface structure and porosity development.

Fatigue strength of a Ti–6Al–4V alloy produced by selective laser melting

The fatigue properties and the fracture mechanisms of the Ti–6Al–4V alloy produced by selective laser melting (SLM) from a powder of an CL41TiELI titanium alloy have been studied. Cylindrical blanks were grown at angles of 90° and 45° to a platform. The best fatigue strength is observed in the samples the blanks of which were grown at an angle of 45°. It is found that the structure of the SLM material can contain portions with unmelted powder particles, which are the places of initiation of fatigue cracks.

Exploitation of Field-Assisted Sintering Technology (FAST) to Produce Pre-Forged Billets from Metastable Beta Titanium Alloy Powder

Powder produced by gas atomisation of metastable beta alloy Ti-5Al-5Mo-5V-3Cr has been consolidated using field-assisted sintering technology (FAST) to examine the suitability of the process to produce pre-forged billets as opposed to the conventional multi-step Kroll-VAR-forging route. FAST testing was performed using an FCT Systeme GmbH spark plasma sintering furnace type HP D 25 at The University of Sheffield. The dwell temperature was varied between 800 and 1200°C and the dwell time between 3 and 60 minutes. The process was found to allow very precise control over the beta grain size in Ti-5Al-5Mo-5V-3Cr by variation of the dwell time and dwell temperature, producing grain sizes between ~40 and ~350 μm. However, it was found that the grain size was increased more by increasing the dwell temperature than increasing the dwell time. The porosity was found to be between 99.5 and 100 % for all dwell temperatures at dwell times of 30 minutes or above. FAST has the ability to produce almost fully consolidated Ti-5Al-5Mo-5V-3Cr pre-forged material from powder with a controlled beta grain size, which is not possible by other methods.

The Application of Direct Metal Laser Sintering (DMLS) of Titanium Alloy Powder in Fabricating Components of Aircraft Structures

This study presents detailed characteristics of the DMLS method as used for titanium alloy powder with reference to a possible intended use in aeronautics applications.In the present study test models were made, designed for trials in which the model material properties are to be determined and which specify the basic features of the RP/DMLS technique. In order to evaluate the ultimate use of the DMLS technique in fabricating titanium alloy parts, the following procedures were conducted: tensile and upsetting tests for Ti6Al4V alloy samples (a comparative analysis for DMLS models and models fabricated, respectively, from titanium sheet and bar was carried out), an SEM analysis of the microstructure of the fragments of the surface of polished and etched samples, a Vickers hardness test and an analysis of the accuracy of the reproduction of the shape and roughness of the model fabricated in the DMLS procedure. A detailed analysis of the DMLS method significantly supplements the existing body of knowledge on innovative rapid prototyping techniques [1–4], and the results allow us to specify a group of aircraft structure components which may be fabricated using this method. Excellent strength properties of DMLS models and the possibility of improving surface quality by mechanical working enable the fabrication of advanced aircraft structure components operated in target conditions (under load).

Structure and machinability of thin-walled parts made of titanium alloy powder using electron beam melting technology

The present study aims at study of structure and properties of raw and thermal treated titanium-based powder material used to produce the thin-walled components by electron beam melting technology. Producing the end product means also studying the finishing cutting process. Examining the quality of end product in terms of geometric tolerance and thin walls thickness stability consists of control the surface roughness is also included in this study.