Introduction to Mechanical Alloying

Abstract

Mechanical alloying is a ball milling process where a powder mixture placed in the ball mill is subjected to high energy collision from the balls. The process is usually carried out in an inert atmosphere. It is an alternative technique for producing metallic and ceramic powder particles in the solid state. The two most important events involved in mechanical alloying are the repeated welding and fracturing of the powder mixture. The alloying process can only be continued if the rate of welding balances that of fracturing and the average particle size of the powders remains relatively coarse (1). Alloys with different combination of elements have been successfully synthesized due to the uniqueness of the process being able to produce new materials from the bottom of the phase diagrams (2). Since mechanical alloying is a solid state process, it provides a means to overcome the drawback of formation of new alloys using a starting mixture of low and high melting temperature elements. Although in general, the raw materials used in mechanical alloying should include at least one fairly ductile metal to act as a host or binder to hold together the other ingredients (3), a lot of studies have confirmed that brittle metals can also be mechanically alloyed to form solid solution (4,5), intermetallics (6) and amorphous alloys as well (7).