Observations of the stress developed in Si inclusions following plastic flow in the matrix of an Al–Si–Mg alloy

Abstract

Measurements are made of the stress developed in near-spherical elastic inclusions in an elastic plastic matrix under both tension and compression loading. Two experimental conditions are reported. The first case is where no thermal mismatch exists between the inclusions and the matrix, so that the stress in the inclusion is purely a result of the misfit in the elastic moduli and of the distortion of the plastic slip-line field around the inclusion. The observations are believed to be the first such and are in qualitative agreement with finite-element modelling for idealised inclusion distributions. The second case is the more usual one where a thermal misfit stress exists and observations are reported of the stress relief effects caused by the interaction of the plasticity-induced stress with the thermal and elastic misfit stresses.

Keywords:

• Residual stress relaxation
• plasticity of metals
• residual stress
• neutron diffraction
• aluminium alloys
• composite materials
• plastic misfit stress

Acknowledgements

We are grateful to the CCLRC for the provision of beam time at the ISIS neutron facility and to General Motors R&D for making the cast plates. Professor Phillip Withers made helpful comments on the manuscript.