strain induced melt activation (SIMA): original concept, its impact and present understanding

The concept of converting dendritic structures into globular morphologies through solid-state deformation, termed as strain-induced melt activation (SIMA), is assessed. Although the original invention defined the specific two-stage deformation scenario, almost four decades of extensive research, involving a variety of ferrous and non-ferrous alloys, subjected to conventional and severe plastic deformations, caused its evolution. According to present understanding, any deformation of cast structures with a strain level sufficient to trigger recrystallisation leads to dendrite-to-globule transition during subsequent partial melting. It is proposed that the SIMA term should not only be associated with the particular deformation scenario but should be seen as a broad synonym for a variety of thermomechanical treatments, explored for controlling the solidification microstructure. Such an updated definition expands applicability of the SIMA concept from bulk billets to coarse particulates and fine powders.