The current status of field assisted sintering technology (FAST) of structural metals from powder is critically reviewed. Recently, there have been significant increases in the uptake of FAST for metallic systems, composites and porous materials at the laboratory-scale. It is clear that FAST is tolerant of powder/particulate feedstock, allowing rapid production of materials, some of which would be challenging through conventional sintering techniques. Yet, the underlying mechanisms allowing this are not fully understood. Final specimen sizes tend to be small, which restricts rigorous mechanical assessment. This review demonstrates the clear benefits in transitioning laboratory-scale demonstrators to the industrial scale over the next few years. However, consideration will need to be given to size, throughput, and shape complexities to attract commercial investment.

Titanium alloys have excellent properties, but components are very expensive due to the high levels of processing required, such as vacuum melting, multi-stage forging, and machining. As a result, forged titanium alloy components are largely exclusive to the aerospace industry, where a high strength-to-weight ratio, corrosion resistance, and excellent fatigue resistance are essential. However, a typical buy-to-fly ratio for such components is approximately 9:1, as much of the forged billet is machined to swarf. The quantity of waste titanium alloy swarf generated is increasing as aircraft orders, and the titanium components contained within them, are increasing. In this paper, waste swarf material has been recycled using the two-step solid-state FAST-forge process, which utilizes field assisted sintering technology (FAST) followed by hot forging. Cleaned Ti-6Al-4V swarf was fully consolidated using the FAST process at sub-transus and super-transus temperatures, followed by hot forging at sub-transus temperatures at different strain rates. It was demonstrated that swarf-derived Ti-6Al-4V FAST billets have equivalent hot forging flow behaviour and resultant microstructures when directly compared to equivalently processed conventional expensive hydride–dehydride powder, and previously reported Kroll-derived melt-wrought material. This demonstrates that titanium swarf is a good quality feedstock for downstream processing. Additionally, FAST-forge is a viable processing route for the closed-loop recycling of machining waste for next-generation components in vehicles and non-aerospace applications, which is game changing for the economics of titanium alloy components.