Synthesis of bulk amorphous and nano-crystalline materials by spray forming

Bulk amorphous and nanocrystalline metallic materials have been observed to possess
excellent mechanical and physical properties. The conventional process routes to synthesize
such materials are restricted by their ability to achieve rapid solidification which limits the
dimensions of the materials produced. In the last ten years, spray forming has been used to
avoid these limitations by using its layer by layer deposition of undercooled droplets. The
available literature indicates that the opportunities provided by this process can be utilized to
produce bulk materials in a single step. In the present paper, an attempt has been made to
review the developments in the area of spray forming of amorphous and/or nanocrystalline
materials. The effect of process parameters, droplet size distribution in the spray, the thermal
conditions of droplets prior to deposition and the deposition surface conditions have been
discussed in detail. It has been demonstrate that the layer by layer deposition of undercooled
droplets of glass forming alloys on a relatively cold deposition surface is the suitable condition
to achieve amorphization/nanocrystallization. A critical analysis of the process parameters and
the results has been made based on the composition, glass forming ability and possible
mechanisms of microstructural evolution.