Abstract: The major reason that there is not more widespread use of titanium and its alloys is the high cost. In this paper, developments in one cost effective approach to fabrication of titanium components - powder metallurgy - will be discussed under various aspects of this technology. The aspects to be discussed are the blended elemental approach, pre-alloyed techniques, additive layer manufacturing, metal injection molding, spray deposition and microwave sintering. A brief review of a number of low cost powder production processes is also presented.
Abstract: In spite of titanium’s excellent combinations of lightweight, mechanical properties, and corrosion resistance it has been excluded from many applications because of its high cost in fabricated componentry. The major cost to produce a titanium alloy component is the processing of the sponge into alloy plus the several processing steps for fabricating the final finished component. If low cost titanium is to become a reality, the cost of post sponge processing to final finished components must be dramatically reduced. Processing to convert sponge directly in one step to an alloyed near net shape low cost component has been demonstrated. The mechanical properties are equivalent to better than standard processed wrought titanium. Example, automotive components and other applications that confirm titanium componentry at substantially lower cost than standard processing will be provided.
Abstract: After evaluating many different routes to produce titanium, the CSIR of South Africa selected a process to produce titanium powder continuously via metallothermic reduction of TiCl4 in molten salt. The project risks are being managed using the well-known STAGE/GATE method. The first two stages, viz, Route Selection and Preliminary Assessment have been completed and the next stage entailing campaigns extending over several days of uninterrupted operation, producing titanium at a rate of about 2 kg/h has recently begun. The rationale for selecting the process route is briefly reviewed and key process problems that had to be solved before embarking on scale-up and measures to do so are explained. Specific problems are: • Feed line blockages, • Titanium product formation and adherence to reactor internals, • Agglomerate formation; and • Production of very fine particles. Lastly the planned schedule and current status of the project are discussed.
Abstract: Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor.
Abstract: Titanium alloy powder provides manufacturing variants to produce a variety of titanium intermediate materials and final products. However, titanium alloy powder is quite expensive at fifteen to thirty times the cost of sponge thus limiting the utilization of titanium powder to produce titanium products. The standard state-of-the-art processing to produce alloy powder results in very high cost of alloy powder. Three new processes have been demonstrated to produce titanium alloy powder at a cost of only 2-5 times the typical cost of sponge. The processes are (1) one step melting of sponge/alloying and gas blowing alloy powder, (2) metallothermic reduction of mixed chloride precursors to produce alloy powder and (3) electrolytic reduction in a fused salt of mixed alloying (TiCl4-AlCl3-VCl4) chlorides. These processes have beeSubscript textn demonstrated to produce low cost titanium alloy powder which can serve as feeds for the variant manufacturing processes to produce low cost titanium products.
Abstract: The CSIRO is developing the TIRO™ process for the continuous direct production of titanium powder. The process comprises two stages. The first stage is a fluidised bed reactor (FBR) in which TiCl4 is reacted with magnesium powder to form solid magnesium chloride particles about 350 µm in diameter in which micron sized titanium particles are dispersed. The second stage is a continuous vacuum distillation operation where the titanium is separated from the magnesium chloride and sintered to form a friable “biscuit”. The biscuit comprises porous titanium spheres about 250 µm in diameter which can be liberated by very light grinding. The overall process has a throughput of 0.2 kg/h Ti, limited by the vacuum distillation unit and is being scaled up. The process has generated Ti powder with ≤0.25 wt% O and < 200 ppm Cl and meets CP2 specifications. Ring grinding the vacuum distilled product for short periods reduced the particle size, however longer grinding times caused agglomeration of the particles. Ring grinding in air resulted in a large increase in oxygen concentration
Abstract: Abstract This paper presents and discusses the factors influencing the yield of Ti-Al alloy in the TiPro process which is a process developed at the University of Waikato for producing titanium alloy powders by mechanically activating Al/TiO2 powder mixtures and subsequently preheating the resultant composite powder in order to ignite a combustion synthesis reaction and separate the liquid Ti-Al alloy by extrusion. In this study, TiO2/Al composite powders with different powder particle microstructures have been produced and used to study the effects of starting composite powder particle microstructure on the solid/liquid separation of TiAl from solid Al2O3 by extrusion. Results obtained so far indicate that maximizing the time the Ti-Al alloy phase is maintained in the liquid state after the reaction between TiO2 and Al is one of the critical factors to increase the yield of Ti-Al alloy produced through the separation of liquid Ti-Al from the solid Al2O3 phase by extruding the mixture of liquid Ti-Al and Al2O3 formed through reactions and heating.
Abstract: The processing of titanium powder has been presumed to have potential to reduce the cost of final parts. The non-melt routes to efficient powder processing require consistent flow, adequate tap density and minimal pick-up of interstitial contaminants. The powder produced by the continuous sodium reduction of titanium tetrachloride has a coral-like morphology and low tap density. In order to achieve the potential of low cost parts, the powder will need to be modified to match the optimum feed conditions of the particular processing technique. The approaches to control interstitial pick-up will be discussed in the context of manufacturing technology: contribution of raw materials (10%), passivation (60%) and densification (30%). A comparison of densification with a change of milling fluid media (argon to water will be made with the unexpected decrease in oxygen pick-up when using water). Powder spheroidization via gas atomization of Armstrong Process® powder will be discussed. The product forms where the advantages of using powder can be exploited have to be carefully selected. Sheet is one such form: the results of using titanium powder to directly make titanium sheet will be presented.
Abstract: Ti-6Al-4V (wt%) alloy rods were prepared successfully using a low-cost method that combines mixing HDH titanium, elemental aluminum and Al-V master alloy powders and powder compact extrusion. The microstructure and mechanical properties of Ti-6Al-4V alloy and the effects of powder compact holding time on them were investigated. The results showed that powder compact holding time had a significant effect on the microstructure and mechanical properties of the extruded Ti-6Al-4V alloy rods. With increasing powder compact holding time from 2 to 10 min., the microstructure of the extruded rods became more homogeneous, and their UTS decreased from 1300 to 1215MPa and the elongation to fracture increased from 7.1 to 10.2%. The tensile properties of the Ti-6Al-4V alloy rods produced by powder compact extrusion of the powder mixture are comparable to those of Ti-6Al-4V alloy produced by ingot metallurgy and thermomechanical processing.