The Mechanical Alloying Process

Abstract

The mechanical alloying/milling process is a solid state powder process where the powder particles are subjected to high energetic impact by the balls in a vial. As the powder particles in the vial are continuously impacted by the balls, cold welding between particles and fracturing of the particles take place repeatedly during the ball milling process. The entire process includes blending of the powder mixture prior to the ball milling, vacuuming and/or filling with protective gases to prevent oxidation and contamination, and the ball milling process itself. Post milling processes after mechanical alloying includes canning, degassing, and finally plastic deformation by extrusion or rolling. The whole process is summarized in Figure 3.1. Before mechanical alloying, it is suggested that the powder particles be blended initially in a blender so that a homogeneous distribution of the different powders can be obtained. For the milling process, several control parameters have to be considered, namely, environment in the vial, ball to powder weight ratio and process control agents.