The following is an excerpt.

Stainless steel is expensive. What if you could get the same user qualities more cheaply by combining a stainless surface with a conventional steel substrate using a surface modification technique? David Embury shares a peek into a new world of hybrid and architectured materials.

Feeling at home: Professor David Embury with steel in the lab at NTNU. Photo: Ole Morten Melgård.
Feeling at home: Professor David Embury with steel in the lab at NTNU. Photo: Ole Morten Melgård.

In the real world, companies like Statoil demand materials that can transport energy. The automotive industry transports people and products. To do so cost effectively, they push conventional materials to the limit. Conflicting properties are required, e.g high strength and high ductility which are difficult to achieve in a single material. Can we take a different approach? Can we combine materials in new geometries and devise new processes to make these architectured materials?


Tailoring Materials and Processes

The idea would be to combine laminated metals, foams and polymers, to modify existing casting and heat treatment processes to produce both hybrid materials and hybrid processes. David Embury exemplifies:

“If you take, say five millimetres of conventional steel and coat it with 100 microns of high chromium steel on the surface to produce an adherent protective oxide, you could save a great deal of money compared to a stainless steel structure.”

At 76, Embury is not only an Honorary Doctor at NTNU; he has just been recruited as member of SFI CASA’s Scientific Advisory Board. This month he gave two lectures in Trondheim: “Do we need homogenous or heterogeneous microstructures?” and “Controlling the competition between plasticity and fracture”.


Relevant to industry

Professor Emeritus from McMaster University in Canada he may be, but far from having curled up in a sofa he still collaborates with researchers around the world. During his stay in Trondheim he talked with people from CASA partner Hydro about the design of aluminium cables for transporting electricity across the deep waters of the North Sea.

“The concept of architectured materials has a lot of relevance to industry. There is great interest in lightweight structural applications for different demands, including energy transport and energy absorption, using architectural materials. Take titanium alloys. If we could make them transform like steels to achieve very high strengths, they would be applicable for a number of new purposes.

The concept of hybrids is known. What we are looking at now, are new combinations of materials and new ways of fabricating complex geometries that is new ways of combining existing knowledge to design new engineering solutions,” Embury says.


Influences CASA

Where predecessor SFI SIMLab became world leaders in the design of crashworthy and protective structures, brand new SFI CASA wants to reach the same level in multi-scale testing, modelling and simulation of materials and structures for industrial applications.

David Embury expects CASA to become more flexible and inclusive than SIMLab was:

“The centre is still in the process of evolving, but the new research field of ultra-high strain testing and the broadening of perspective with glass is likely to increase the social impact. One example is that work on glass in buildings also will be interesting for glass in cars and other forms of transport.”

Without knowing, Embury confirms the interest Honda’s Eric DeHoff showed at CASA’s kick-off, where he made exactly the same point. Since then, other CASA partners have expressed the same interest.


Intelligent materials

CASA’s Scientific Advisory Board (SAB) hasn’t had its first meeting yet, but David Embury served on SIMLab’s SAB as well. He would like to contribute to CASA’s future activities:

“CASA can clearly utilize the experience of SIMLab in encouraging inclusion of more partners. CASA should also build on SIMLab’s strength in the interface between mechanics and materials. Then all kinds of things might emerge, such as a variety of intelligent materials. The social relevance of the products will increase with the combination of glass and polymers.”

“So who would you welcome as new partners?”

“I would be happy to see a big glass producer on board. A broadening of large producers would be valuable for all,” he says. He thinks CASA’s portfolio may change more rapidly than did SIMLab’s, with a broader range of applications where products can be applied.


Research voids

David Embury sees some challenges ahead:

“There is almost no modern steel research at NTNU. There is enormous use of steel in the Norwegian economy but very little basic understanding. CASA should develop input in this area. It may not be found in Norway, but certainly in Sweden and Finland. Norway produces resources like aluminium and fish, but what do you buy? The material bills for infrastructure must be enormous, yet the basic knowledge of structural materials other than aluminium in the Norwegian system is very limited. You could compare it to a situation where in France, which depends heavily on nuclear power, and thus needs a broad knowledge of uranium and of pressure vessel steels suitable for nuclear applications knew nothing about uranium.”


Avoid overload

The scientific advisor has one more piece of advice:

“CASA is going to need good postdoctoral staff and visiting faculty. You have very good students, but will need to increase the manpower in the system with people from all over the world. I am concerned that you do not increase the load on faculty. They should remain truly productive and not overloaded as they are in many North American universities.”

PS: The original title of this article was “How to replace Stainless Steel with Foam”. David Embury has asked us to correct to the present “How to replace Stainless Steel with a Hybrid”, which is more correct.