IFM researchers are developing novel methods to upcycle metal alloys and thus address the major issue of waste in the industry.
Titanium has a low density and is well known for its high strength to weight ratio. An estimated 75% of titanium (Ti) metal is used in aerospace applications, with the remaining 25% used in armour, chemical processing, marine hardware, medical implants, power generation, sporting goods and other applications.
Titanium components account for up to 15% of the total weight of modern aircraft. However, up to 90% of the original titanium (158,000 tons) for aerospace applications is left over as waste chips (swarf) during the entire manufacturing process.
World titanium production in 2017 was 223,000 metric tons. Assuming an average market purchase price of $11.20 per kilogram, the value of wasted titanium from aerospace applications alone is about $165 million. But only a fraction of this scrap metal is recycled. (In 2017, 50,000 tons of scrap metal was recycled by the titanium industry, 11.000 tons by the steel industry, 1.1000 tons by the superalloy industry, and 1,000 by other industries globally).
Existing industry problem
The increasing application of titanium alloys in the aerospace industry leads to huge losses of metals in the form of swarf. In some instances, as much as 50-90% of the part’s weight ends up as swarf. Some investigations have revealed that the machining industry converts about 10% of all the metal produced into machining chips. Most recently, it has been found that in biomedical applications, a typical Ti alloy knee implant component machined from a bar stock results in as much as 80% of material wasted in the form of swarf. Traditional recycling methods for titanium swarf involves the process of re-melting and re-casting, which requires high energy consumption and protective environments. Moreover, swarf is contaminated with coolants and lubricants, or mixed with foreign substances, and the cost of recycling this waste is prohibitive, therefore there exists an opportunity for the development of an innovative process to convert the swarf to bulk titanium or titanium powder for additive manufacturing.
Our research solution
Traditionally, recycling of Ti swarf has been a very expensive process. Hence, developing innovative processes to recycle Ti alloy swarf or even better, to upcycle Ti alloys, i.e. produce the bulk material with better mechanical properties compared to initial Ti alloy, is becoming increasingly important.
IFM researchers led by A/Prof Rimma Lapovok and Dr Ilana Timokhina are investigating the use of titanium swarf as a potential precursor to manufacture bulk ultrafine grains or multicomponent materials with high density and strength.
They are using a novel approach of swarf compaction by severe shear deformation under high hydrostatic pressure to upcycle the waste titanium into high-value materials. The mechanical properties of the compacted swarf are even better than properties of similar processed alloy.
In a second approach, they are also developing a method for using titanium swarf to produce high quality powder (small size, good size distribution, low level of contamination and spherical shape) for additive manufacturing of parts for aerospace and biomedical applications.