Abstract
Titanium-tantalum alloys have historically been difficult to produce using conventional techniques due to the large difference in melting point and poor interdiffusivity rates of the two elements, leading to large levels of segregation. In this work we have investigated using the Metalysis-FFC process to overcome this problem. The Metalysis-FFC process is an electrochemical process where metal oxides are reduced by acting as a cathode in an electrolytic cell combined typically with a graphite anode and molten calcium chloride electrolyte. Previous work has proven that the process works when applied to mixed oxides to produce alloys. The reduction process is performed in the solid state and so negates the problems associated with traditional melting practices such as segregation and evaporation losses. In this work we have been able to successfully produce a range of Ti-Ta alloy powders from pure titanium to pure tantalum in 10 wt% increments using the Metalysis-FFC process. Moreover, energy dispersive spectroscopy analysis of the powders suggests uniform distribution of titanium and tantalum within all compositional ranges, suggesting the Metalysis-FFC process has the potential to be a transformative manufacturing methodology for producing titanium-tantalum alloys.
Highlights
Tantalum possesses a range of properties that make it desirable for use as a refractory metal such as a high melting point (3017 °C), good ductility and chemical inertness
The aim of this study is to explore the production of tantalum and titanium-tantalum alloys via the direct electrochemical reduction of tantalum pentoxide by utilising the Metalysis-FFC process
Analysis by Scanning Electron Microscopy (SEM) shows a two-phase microstructure which is typical of an α+β titanium alloy and is in agreement with the phase diagram published in the literature [1]
Summary
Tantalum possesses a range of properties that make it desirable for use as a refractory metal such as a high melting point (3017 °C), good ductility and chemical inertness. The major use of tantalum is currently in the electronics industry as a material for capacitors It is used in small quantities as an alloying addition in specialist alloys. The unique properties of tantalum as a bulk material are yet to be fully exploited; this is in part due to the cost of extraction from its ore and the difficulty of alloying due to its high melting point. Another disadvantage of tantalum is its high density (16.7 g.cm-3); a way to overcome this is to alloy it with a lightweight material such as titanium. The phase diagram of the titanium-tantalum system shows full solubility of the two metals with two distinct phases (Figure 1); it should be possible to produce alloys with an even distribution of both elements
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