University UK
1. Summary
The potential global economic impact of nanostructured materials and their processing by 2011 is estimated at $340 billion (Hitachi Research Institute). This includes nanopowders and nanocoatings, which are relatively well established. As far as bulk nanometals are concerned there are two main routes available. The powder metallurgy (PM) route is technically, environmentally and economically problematic because it uses nanopowders. Another route is based on severe plastic deformation (SPD) of metals, which subdivides original coarse grains into much smaller grains. The SPD route avoids many of the problems associated with the PM route. It enables processing of all kinds of common metals using a new class of metal working processes, which do not change the shape of the metal billet. However, none of these processes have been proven on an industrial scale.
2. Commercial prospects
Compared to common metals with the grain size of tens or hundreds of μm, , also known as nanocrystalline metals or nanometals, have the grain size reduced to about 0.1-1 μm. This structural change affects many mechanical and physical properties of UFG metals, for example, their strength and hardness can be increased two to five times with a relatively small or no reduction of ductility. Some metals, like cast magnesium, become stronger and more ductile. UFG metals excel at cryogenic temperatures, while at elevated temperatures they posses largely improved superplastic properties. The components made of UFG metals can be substantially stronger and/or lighter. These features should appeal to many modern industries including manufacturers of automotive parts, metal microparts for microsystems, parts for the aerospace industry, medical devices, defence systems and sports equipment.
• The first commercial application of bulk UFG metals was in sputtering targets for physical vapour deposition to be used for metallization of silicon wafers (Honeywell Electronic Materials). Compared to normal coarse grain sputtering targets, the life span of sputtering targets made of UFG metals can be increased by 30 % and the quality of coating can be improved (more uniform coating). The global market value of the sputtering target industry is estimated to reach $1,800 million in 2006.
• The next highly anticipated application should be that of medical implants, where nanostructured pure titanium could replace less biocompatible titanium alloys.
• Another potential winner is the superplastic forming industry, which is confined to low volume production because of a very low forming speed required for the classical superplastic metals. UFG metals possess better superplastic properties, which allow a tenfold increase of the forming speed and/or temperature reduction.
• The automotive industry could become a major customer for these new less expensive superplastically formed parts. Equally useful for this sector, UFG aluminium fasteners, and self-piercing rivets in particular, can be made strong enough to replace steel fasteners used in aluminium car bodies in order to avoid galvanic corrosion.
• Lighter armour for military vehicles and personnel could be another application of UFG metals. UFG metals are also considered for projectiles. There is evidence that UFG tungsten exhibits self-sharpening properties, which could make it an attractive alternative to the controversial depleted uranium projectiles.
• Users of sports equipment will also benefit from UFG metals, particularly where high strength and low weight is required. UFG metals could find applications in, for example, high performance bicycles, sailing equipment, mountaineering equipment and golf. In this context, an additional advantage of UFG metals is their improved vibration damping capability.
• Among many interesting properties of UFG metals is their ability to flow easier and at lower temperatures when forged into complex shapes. It is claimed that energy savings up to 30% could be achieved due to: lower forging temperature, shorter heat-up time, smaller forging stock size, fewer number of hits and lower forging load.
• A very small grain size can be a virtue of its own. This is the case with metal microparts with the geometrical sizes (< 1mm) comparable with coarse grains of the classical materials. UFG metals make these parts behave as their macro counterparts. This refers both to the inner body and the surface of the part. Other anticipated advantages of UFG surfaces are better optical-quality metal surfaces produced by machining and also general-purpose eroded surfaces.
3. Infrastructure/facilities
In 2003, the researcher received funding for developing new and industrially viable SPD processes. This resulted in the development of a 3D-ECAP (equal channel angular pressing) process, for which a patent application has been filed. 3D-ECAP is a batch process, which can produce short billets of UFG metals. There will be cases when a batch process is technically justified and economically viable. However, for high volume production, a continuous process would be more appropriate. Such a process is currently being developed and a patent application being prepared. The development work so far was carried out at a laboratory level. For this, laboratory machinery and tooling were sufficient. Finite Element Method (FEM) simulation was extensively used for process development and optimisation. Materials’ testing was carried out at the University, while microstructure observations were outsourced.
4. Critical issues
There are no large scale commercial activities involving SPD-made UFG metals yet. However, there is evidence that such activities are being promoted by research teams from the US, Russia, Korea and other countries. A good indication of commercialisation possibilities is the number of the SPD-related patents and patent applications, which has reached 65 (Terry C. Lowe, NanoSPD3, Fukuoka, 2005). Having developed some original SPD processes and technological know-how, Dr Rosochowski considers commercialisation of the SPD technology as an important aspect of his research; commercial applications provide focus and the means to perform research. For this to happen, two types of activities are necessary - dissemination of knowledge about UFG metals among potential end-users and protecting IPR in those cases when information exchange develops into commercial cooperation. More practically, end-users of UFG metals will need a reliable and consistent supply of these materials, while the producers of UFG metals will need an appropriate, possibly continuous SPD process and a machine tool capable of realising it. Thus, the critical issues regarding further development of the SPD technology are:
(1) Identification of potential end-users of UFG metals,
(2) Funding research on the identified applications (production of laboratory samples of UFG metals, optimisation of process parameters, materials and application testing),
(3) Developing a prototype machine for a continuous SPD process (in case larger quantities and dimensions of UFG billets are required for testing),
(4) Establishing a production unit capable of meeting a growing (hopefully) demand for UFG metals,
(5) Securing IP rights by patenting the developed ideas.
