Surfactants in Mechanical Alloying/Milling: A Catch-22 Situation

Mechanical alloying/milling technique is characterized by the repeated welding and fracturing of powder particles in a high-energy ball mill, which often results in excessive cold welding and agglomeration of ductile particles. To achieve the critical balance between cold welding and fracturing, the surface of the deforming particles is modified by introducing a suitable organic material, called surfactant or process control agent (PCA). However, the use of surfactants is self-contradictory by nature and requires further consideration of the milling variables and type/amount of surfactant. The current article provides a practical approach to the promises and challenges associated with surfactants in mechanical alloying/milling. An attempt has been made to address the most crucial aspects correlated with surfactants, including contamination, the morphology and size of powder particles, formation of alloy and microstructural evolution, and powder yield, as well as the physico-mechanical properties, such as magnetism, density, hardness, and compressive strength. An overview is also given on the adsorption mechanism of surfactants onto the surface of powder particles, with a special emphasis on type, amount, and the addition time of surfactants in the mechanical alloying process.