Direct reduction of synthetic rutile using the FFC process to produce low-cost novel titanium alloys

Abstract

Typically, pure TiO 2 in pellet form has been utilised as the feedstock for the production of titanium metal via the solid state extraction FFC process. For the first time, this paper reports the use of loose synthetic rutile powder as the feedstock, along with its full characterisation at each stage of the reduction. The kinetics and mechanism of the reduction of synthetic rutile to a low oxygen titanium alloy have been studied in detail using a combination of X-ray diffraction, scanning electron microscopy, oxygen analysis, and X-ray fluorescence techniques. Partial reductions of synthetic rutile enabled a reaction pathway to be determined, with full reduction to a low oxygen titanium alloy occurring at 16 h. Major remnant elements from the Becher process within the feedstock were followed throughout the process, with a particular emphasis placed on the reduction behaviour of iron within the alloy. Although impurities such as Fe, Al, and Mn are found in the feedstock and alloy, no major deviations from previously reported reaction mechanisms and phase transformations utilising a pure porous (25-30 % porosity) TiO 2 precursor were found. Following reduction, the titanium alloy powder produced from synthetic rutile (approx. 3500 ppm oxygen) has been consolidated via an emerging rapid sintering technique, and its microstructure analysed. This work will act as the baseline for future alloy development projects aimed at producing low-cost titanium alloys directly from synthetic rutile. Producing titanium alloys directly from synthetic rutile may negate the use of master alloy additions to Ti in the future.

Development of the Fray-Farthing-Chen Cambridge Process: Towards the Sustainable Production of Titanium and Its Alloys

“…S3a and S3b show the microstructures of the ground natural ilmenite feedstock before and after electroreduction, respectively. 66 More recently, low-cost and novel titanium alloys were produced directly from either synthetic rutile (i.e., rutile produced from ilmenite, with a transition metal element concentration of 3.7% and aluminium content below 1%), 21,67 or naturally occurring rutile ore (beach sand) 20 via the FFC-Cambridge process (see supplementary Fig. S3c and S3d).…”

“…S3c and S3d). 67 The obtained titanium alloy powder was spheroidised, and fabricated into a billet via hot isostatic pressing (HIP) and subjected to monotonic tensile testing. 20 The test result revealed that the ultimate tensile strength of this material is close to that of Ti-6Al-4V.…”

Carbon Dioxide (CO₂) Released in the Electrochemical Reduction of Titanium Dioxide (TiO₂) to Titanium Metal

“…However, the actual mechanism of conversion of TiO 2 to titanium metal appears to be more complex with formation of several sub-oxides of titanium and calcium titanate as intermediate reaction species 4,5) . It has been convincingly explained that the calcium metal deposited (due to the electrolysis of CaO dissolved in the CaCl 2 electrolyte), on the cathode (TiO 2 ) can reduce the oxide into metal through various intermediate titanium suboxides.…”

On a Testing Methodology for the Mechanical Property Assessment of a New Low-Cost Titanium Alloy Derived from Synthetic Rutile

“…Following reduction of SR an a + b type titanium alloy is produced, without the cost of alloying additions. [7] Hence, the use of SR as a feedstock is notably cost-effective, as not only are feedstock costs reduced, but the dependency on master alloy additions further downstream is reduced or eliminated.…”

“…SR-derived alloys have previously been consolidated to 98.6 pct density but no mechanical properties have been reported. [7] With respect to morphology, Ti-64 is angular, due to its production via HDH processing (Figure 3(c)). Table I provides details of the SR-derived titanium alloy and commercial Ti-64.…”