Nanostructured Materials and Nanocomposites by Mechanical Alloying: An Overview

The technique of mechanical alloying, although originally developed to produce oxide-dispersion-strengthened superalloys for aerospace and high-temperature applications, is now recognized as an important and versatile technique to synthesize metastable and advanced materials with a high potential for widespread applications. Mechanical alloying involves repeated cold welding, fracturing, and rewelding of powder particles in a high-energy ball mill. The reduced diffusion distances between metal powder layers formed as a result of heavy deformation, introduction of a high density of crystal defects, and a slight rise in powder temperature contribute to alloy formation from blended elemental powders. The type of phases/materials produced by mechanical alloying of powder mixtures include supersaturated solid solutions, intermetallics, quasicrystalline alloys, high-entropy alloys, amorphous alloys, and composites. If the material produced is crystalline in nature, most often the grain size is in the nanometer size. Amongst these phases, nanostructured materials and nanocomposites have been the most important types investigated. In this contribution, we will present an overview of the processing, characteristics, and properties of nanocrystalline materials and nanocomposites produced by mechanical alloying, with special emphasis on our recent work. Graphical abstract