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

Abstract

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.