Evolution of mechanical response and dislocation microstructures in small-scale specimens under slightly different loading conditions

Abstract

In small dimensions, the flow stress of metallic samples shows a size-dependence such that smaller is stronger, even in nominally strain gradient-free loading conditions. However, the role of the boundary conditions in miniaturised tension or compression tests on the mechanical response and dislocation structure has not been studied in detail. In simulations performed with a three-dimensional discrete dislocation dynamics tool, initial, well-defined dislocation microstructures are loaded in tension with different boundary conditions including superimposed torsion moments. The influence of the loading conditions on details of the evolving dislocation microstructure was investigated by using identical starting configuration. An additional torsion moment significantly influences the dislocation activity since forest-dislocations are generated, but size effect of the flow stress is found to be unchanged.

Keywords:

• dislocation structures
• micro samples
• simulation
• boundary conditions
• dislocation dynamics

Acknowledgements

The financial support of the European Commission NANOMESO Project under contract number NMP3-CT-2006-016710 and Deutsche Forschungsgemeinschaft (DFG) under project Gu367/18-2 is gratefully acknowledged.