Mechanical alloying (MA) is a powder process that consists of repeated cold welding

fracturing

and rewelding of powder particles in a high-energy ball mill. This process is capable of synthesizing different types of non-equilibrium phases including supersaturated solid solutions

nanocrystalline materials

metallic glasses

high-entropy alloys

and several others. MA'd materials have found many applications. The present article critically reviews recent developments in emerging areas of nanostructured materials and nanocomposites

high-entropy alloys

alloys synthesized from immiscible elements

and heterostructured materials. Current challenges and future directions of research in the general area of MA are also indicated.