Abstract
In order to provide further evidence of damage mechanisms predicted by the recent solid-state transformation creep (SSTC) model, direct observation of damage accumulation during creep of Al–3.85Mg was made using synchrotron X-ray refraction. X-ray refraction techniques detect the internal specific surface (i.e. surface per unit volume) on a length scale comparable to the specimen size, but with microscopic sensitivity. A significant rise in the internal specific surface with increasing creep time was observed, providing evidence for the creation of a fine grain substructure, as predicted by the SSTC model. This substructure was also observed by scanning electron microscopy.
Highlights
Cavities and pores are present in metallic materials from their manufacture (Toda et al, 2013; Kassner & Hayes, 2003), it is well established that creep introduces further significant damage
We demonstrate that the present observations are in agreement with the damage accumulation that is predicted in the recent solid-state transformation creep (SSTC) model based on isothermal transformation processes (Fernandez et al, 2016)
Synchrotron X-ray refraction proved to be a useful technique to quantitatively determine the evolution of damage during creep
Summary
Cavities and pores are present in metallic materials from their manufacture (Toda et al, 2013; Kassner & Hayes, 2003), it is well established that creep introduces further significant damage. Several mechanisms that control cavity growth have been suggested: grain-boundary diffusion, grain-boundary sliding, constrained diffusion and plastic deformation (Toda et al, 2013). This special structure should influence the spatial and size distribution of cavities. No direct observation of damage accumulation has been provided in the Al–Mg system (Yavari et al, 1981)
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