Mechanical alloying and milling

Mechanical alloying (MA) is a solid-state powder processng technique involv ing repeated welding, fracturing, and rewelding of powder particles in a hi gh-energy ball mill. Originally developed to produce oxide-dispersion stren gthened (ODS) nickel- and iron-base superalloys for applications in the aer ospace industry, MA has now been shown to be capable of synthesizing a vari ety of equilibrium and non-equilibrium ahoy phases starting from blended el emental or prealloyed powders. The non-equilibrium phases synthesized inclu de supersaturated solid solutions, metastable crystalline and quasicrystall ine phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of p owder contamination has been analyzed and methods have been suggested to av oid/minimize it. The present understanding of the modeling of the MA proces s has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product ph ases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.