Grain size effects in the deformation of polycrystalline iron

High-purity polycrystalline iron of two different grain sizes was deformed at room temperature in tension to strains of up to 0.27, and the deformation mechanisms operative at selected strain levels identified by examining both the bulk microstructure by transmission electron microscopy and features developed on prepolished surfaces using optical microscopy.

It was found that the operative mechanisms differed with grain size, there being more inhomogeneous deformation (especially the development of deformation banding and microscopic shear bands) in the finer grain size material. For both grain sizes, most of the observed effects levelled off at strains of ∼0.12–0.15; this is attributed to the onset of dynamic recovery.