Materials with very small grain size – nano- and submicrocrystalline – demonstrate attractive mechanical properties and unusual deformation behavior. Our aim is to propose physical mechanisms explaining it, and to develop new materials with enhanced mechanical properties.
In this research work the following investigators are involved: Horst Hahn, Julia Ivanisenko, Askar Kilmametov, Roman Kulagin, Dayan Nugmanov, Jiamin Hu and Sree Harsha Nandam.
At INT nanostructured materials are produced using various methods: „bottom-up“ like inert gas condensation and layer deposition, and “top-down” approach based on the severe plastic deformation (SPD) for microstructure refinement. In particular, Christian Kübel Research Group.has been recently established at INT as the SPD technique for the synthesis of nanostructured metals and alloys possessing sub-micron or even nanometer-sized grains. For many alloys HPT offers a powerful tool for microstructure design on different hierarchical levels. This includes, in addition to grain size refinement, grain boundary design, texture formation, mechanically driven phase transformation, and the formation of metastable phases. In order to study mechanical properties we use specially designed for miniature specimens and equipped with laser extensometer for precise strain measurement. Characterization of the samples microstructure is performed using XRD analysis and a in collaboration with
Figure 1. (a) Schematic diagram explaining the principle of high pressure torsion; (b) Tensile “Engineering stress – Strain” curve of HPT-processed Pd-20%Ag alloy. Grain refinement down to 120 nm, as shown in the dark field TEM image in insert, resulted in the increase of strength for six times as compared with coarse grained state. For details see
- Grain refinement and mechanical properties in ultrafine grained Pd and Pd – Ag alloys produced by HPT
L. Kurmanaeva, Yu. Ivanisenko, J. Markmann, C. Kübel, A. Chuvilin, S. Doyle,
R.Z. Valiev, H.-J. Fecht Mat. Sci. Eng. 2010,A 527:1776–1783.
1. Scaling up of High Pressure Torsion
2. Mechanical behavior of nanoglasses
3. Mechanically driven phase transformations
4. Mechanical behavior and deformation mechanisms of nanocrystalline metals and alloys
5. Mechanical properties of nanocrystalline carbon steels under static and cyclic load