Chris Hulme-Smith B.A.,M.Sci. (Cantab)

University of Cambridge
Materials Science and Metallurgy
Pembroke Street, Cambridge CB2 3QZ, U. K.
+44 (0)1223 334495

Chris Smith

Thermal Stability of Retained Austenite in Bulk Nanocrystalline Steels

Over the past decade there has been much research into a novel class of steels which contain grains that are tens of nanometres in size. This is achieved by allowing the steel to transform to bainite at very low temperatures, giving a structure of alternating films of bainitic ferrite and retained austenite known as Superbainite. The ultra-fine grain size gives these steels extraordinary strength and hardness, and the presence of retained austenite provides toughness and ductility. This combination of properties could allow superbainite to replace other materials for engineering applications and thereby reduce materials and energy consumption.

Presently, the low bainite transformation temperature is achieved by adding a large amount of carbon to the steel, which is concentrated in the austenite as the bainitic ferrite grows. This renders the austenite thermodynamically unstable and, when it is tempered, the austenite decomposes to produce a brittle combination of martensite and cementite. This limits bulk nanocrystalline steels to low temperature applications, such as armour. In order for the steel to be used at elevated temperatures, such as in engines, the austenite stability must be improved.

I am currently working to improve this stability using a combination of computer modelling and experimental measurements. Work within the Phase Transformations and Complex Properties Research Group has demonstrated that this approach is viable and I am continuing to investigate further refinements to improve the long-term durability of these steels at elevated temperatures.

The project is funded by Rolls-Royce Group plc in conjunction with the Engineering and Physical Sciences Research Council (EPSRC).

Other Interests

I am particularly interested in materials and energy sustainability, especially future power generation. I undertook my final year project within the Device Materials Group here in Cambridge where I worked on a low-energy production route for zinc oxide nanorods for use in inorganic solar cells. The potential of bulk nanocrystalline steels to both replace other materials and reduce materials and energy consumption is one of the reasons I chose to undertake my current research.

Away from Materials Science, I have rowed for Peterhouse Boat Club and (recently) I have started to play golf.


PT Group Materials Algorithms Materials Science and Metallurgy