The University of Southampton
Engineering and the Environment

Research project: Strengthening of alloys by refining grains to the nanometer scale

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Processing of metallic alloys through severe plastic deformation (SPD) promises the creation of a new class of materials that have a combination of beneficial properties, such as ultra high formability, high specific strength, high toughness and high electrical and thermal conductivity.  Key to the improved properties is the creation of a nanosized structure and stresses and strains in the material at the nanometer scale.

Project Overview

In the search for materials with improved mechanical properties severe plastic deformation (SPD) has attracted wide attention due to the strength increase that can surpass that of the strongest steels. The strength increase is mostly due to the creation of stresses and strains in the material at the nanometer scale. These stresses and strains are related to local imperfections in the lattice called dislocations. In addition also the strong refinement of the grains contributes to strengthening. To fully exploit the capabilities of SPD we need models that are able to predict these structures and predict the resulting mechanical properties. The work of a group of researchers led by Prof Marco Starink is dedicated to this research. The work has involved several PhD students and international collaborations with researchers in the US, India, China, Norway and Australia.

Transmission electron microscopy images of a 7xxx series aluminium alloy before severe plastic deformation by high pressure torsion
Before deformation
Transmission electron microscopy images of a 7xxx series aluminium alloy after severe plastic deformation by high pressure torsion
After deformation

 

 

 

 

 

 

 

 

 

 

The picture on the left shows the triple point of 3 grains which are several micrometers in size with very limited deformation. (Deformation is evidenced by the few bands of contrast and dislocation lines.)

The picture on the right shows very small grains (about 0.1 micrometer= 100 nanometers), with evidence of high local deformation.

Associated research themes

Materials and Surface Engineering

Related research groups

Engineering Materials
Schematic diagram of HPT machine
Schematic diagram of HPT machine

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