Novel materials synthesis by mechanical alloying/milling

An account is given of the research that has been carried out on mechanical alloying/milling (MA/MM) during the past 25 years. Mechanical alloying, a high energy ball milling process, has established itself as a viable solid state processing route for the synthesis of a variety of equilibrium and no n-equilibrium phases and phase mixtures. The process was initially invented for the production of oxide dispersion strengthened (ODS) Ni-base superall oys and later extended to other ODS alloys. The success of MA in producing ODS alloys with better high temperature capabilities in comparison with oth er processing routes is highlighted. Mechanical alloying has also been succ essfully used for extending terminal solid solubilities in many commerciall y important metallic systems. Many high melting intermetallics that are dif ficult to prepare by conventional processing techniques could be easily syn thesised with homogeneous structure and composition by MA. It has also, ove r the years, proved itself to be superior to rapid solidification processin g as a non-equilibrium processing tool. The considerable literature on the synthesis of amorphous, quasicrystalline, and nanocrystalline materials by MA is critically reviewed. The possibility of achieving solid solubility in liquid immiscible systems has made MA a unique process. Reactive milling h as opened new avenues for the solid state metallothermic reduction and for the synthesis of nanocrystalline intermetallics and intermetallic matrix co mposites. Despite numerous efforts, understanding of the process of MA, bei ng far from equilibrium, is far from complete, leaving large scope for furt her research in this exciting field.